diff --git a/internal/fakechain/fakechain.go b/internal/fakechain/fakechain.go
index cbf5b95cb..9d89e91d2 100644
--- a/internal/fakechain/fakechain.go
+++ b/internal/fakechain/fakechain.go
@@ -290,7 +290,7 @@ func (chain *FakeChain) GetStateRoot(height uint32) (*state.MPTRootState, error)
 }
 
 // GetStorageItem implements Blockchainer interface.
-func (chain *FakeChain) GetStorageItem(id int32, key []byte) *state.StorageItem {
+func (chain *FakeChain) GetStorageItem(id int32, key []byte) state.StorageItem {
 	panic("TODO")
 }
 
@@ -300,7 +300,7 @@ func (chain *FakeChain) GetTestVM(t trigger.Type, tx *transaction.Transaction, b
 }
 
 // GetStorageItems implements Blockchainer interface.
-func (chain *FakeChain) GetStorageItems(id int32) (map[string]*state.StorageItem, error) {
+func (chain *FakeChain) GetStorageItems(id int32) (map[string]state.StorageItem, error) {
 	panic("TODO")
 }
 
diff --git a/pkg/compiler/syscall_test.go b/pkg/compiler/syscall_test.go
index fdb2f7228..ace3adb1b 100644
--- a/pkg/compiler/syscall_test.go
+++ b/pkg/compiler/syscall_test.go
@@ -98,7 +98,6 @@ func TestSyscallExecution(t *testing.T) {
 		"storage.GetContext":                 {interopnames.SystemStorageGetContext, nil, false},
 		"storage.GetReadOnlyContext":         {interopnames.SystemStorageGetReadOnlyContext, nil, false},
 		"storage.Put":                        {interopnames.SystemStoragePut, []string{sctx, b, b}, true},
-		"storage.PutEx":                      {interopnames.SystemStoragePutEx, []string{sctx, b, b, "storage.PutConstant"}, true},
 		"storage.ConvertContextToReadOnly":   {interopnames.SystemStorageAsReadOnly, []string{sctx}, false},
 		"crypto.ECDsaSecp256r1Verify":        {interopnames.NeoCryptoVerifyWithECDsaSecp256r1, []string{b, pub, sig}, false},
 		"crypto.ECDsaSecp256k1Verify":        {interopnames.NeoCryptoVerifyWithECDsaSecp256k1, []string{b, pub, sig}, false},
diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 1ed1d8665..988b864f4 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -1124,12 +1124,12 @@ func (bc *Blockchain) GetAppExecResults(hash util.Uint256, trig trigger.Type) ([
 }
 
 // GetStorageItem returns an item from storage.
-func (bc *Blockchain) GetStorageItem(id int32, key []byte) *state.StorageItem {
+func (bc *Blockchain) GetStorageItem(id int32, key []byte) state.StorageItem {
 	return bc.dao.GetStorageItem(id, key)
 }
 
 // GetStorageItems returns all storage items for a given contract id.
-func (bc *Blockchain) GetStorageItems(id int32) (map[string]*state.StorageItem, error) {
+func (bc *Blockchain) GetStorageItems(id int32) (map[string]state.StorageItem, error) {
 	return bc.dao.GetStorageItems(id)
 }
 
diff --git a/pkg/core/blockchainer/blockchainer.go b/pkg/core/blockchainer/blockchainer.go
index 24ed60289..be17fd192 100644
--- a/pkg/core/blockchainer/blockchainer.go
+++ b/pkg/core/blockchainer/blockchainer.go
@@ -56,8 +56,8 @@ type Blockchainer interface {
 	GetStandByValidators() keys.PublicKeys
 	GetStateProof(root util.Uint256, key []byte) ([][]byte, error)
 	GetStateRoot(height uint32) (*state.MPTRootState, error)
-	GetStorageItem(id int32, key []byte) *state.StorageItem
-	GetStorageItems(id int32) (map[string]*state.StorageItem, error)
+	GetStorageItem(id int32, key []byte) state.StorageItem
+	GetStorageItems(id int32) (map[string]state.StorageItem, error)
 	GetTestVM(t trigger.Type, tx *transaction.Transaction, b *block.Block) *vm.VM
 	GetTransaction(util.Uint256) (*transaction.Transaction, uint32, error)
 	SetOracle(service services.Oracle)
diff --git a/pkg/core/dao/cacheddao_test.go b/pkg/core/dao/cacheddao_test.go
index ee8211ade..db45c7cb1 100644
--- a/pkg/core/dao/cacheddao_test.go
+++ b/pkg/core/dao/cacheddao_test.go
@@ -32,15 +32,15 @@ func TestCachedCachedDao(t *testing.T) {
 
 	id := int32(random.Int(0, 1024))
 	key := []byte("qwerty")
-	si := &state.StorageItem{Value: []byte("poiuyt")}
+	si := state.StorageItem("poiuyt")
 	require.NoError(t, ccdao.PutStorageItem(id, key, si))
 	resi := ccdao.GetStorageItem(id, key)
 	assert.Equal(t, si, resi)
 
 	resi = cdao.GetStorageItem(id, key)
-	assert.Equal(t, (*state.StorageItem)(nil), resi)
+	assert.Equal(t, state.StorageItem(nil), resi)
 	resi = pdao.GetStorageItem(id, key)
-	assert.Equal(t, (*state.StorageItem)(nil), resi)
+	assert.Equal(t, state.StorageItem(nil), resi)
 
 	cnt, err := ccdao.Persist()
 	assert.NoError(t, err)
@@ -48,7 +48,7 @@ func TestCachedCachedDao(t *testing.T) {
 	resi = cdao.GetStorageItem(id, key)
 	assert.Equal(t, si, resi)
 	resi = pdao.GetStorageItem(id, key)
-	assert.Equal(t, (*state.StorageItem)(nil), resi)
+	assert.Equal(t, state.StorageItem(nil), resi)
 
 	cnt, err = cdao.Persist()
 	assert.NoError(t, err)
diff --git a/pkg/core/dao/dao.go b/pkg/core/dao/dao.go
index b7ad486a5..af40a37f6 100644
--- a/pkg/core/dao/dao.go
+++ b/pkg/core/dao/dao.go
@@ -48,9 +48,9 @@ type DAO interface {
 	GetNEP17TransferLog(acc util.Uint160, index uint32) (*state.NEP17TransferLog, error)
 	GetStateRoot(height uint32) (*state.MPTRootState, error)
 	PutStateRoot(root *state.MPTRootState) error
-	GetStorageItem(id int32, key []byte) *state.StorageItem
-	GetStorageItems(id int32) (map[string]*state.StorageItem, error)
-	GetStorageItemsWithPrefix(id int32, prefix []byte) (map[string]*state.StorageItem, error)
+	GetStorageItem(id int32, key []byte) state.StorageItem
+	GetStorageItems(id int32) (map[string]state.StorageItem, error)
+	GetStorageItemsWithPrefix(id int32, prefix []byte) (map[string]state.StorageItem, error)
 	GetTransaction(hash util.Uint256) (*transaction.Transaction, uint32, error)
 	GetVersion() (string, error)
 	GetWrapped() DAO
@@ -61,7 +61,7 @@ type DAO interface {
 	PutCurrentHeader(hashAndIndex []byte) error
 	PutNEP17Balances(acc util.Uint160, bs *state.NEP17Balances) error
 	PutNEP17TransferLog(acc util.Uint160, index uint32, lg *state.NEP17TransferLog) error
-	PutStorageItem(id int32, key []byte, si *state.StorageItem) error
+	PutStorageItem(id int32, key []byte, si state.StorageItem) error
 	PutVersion(v string) error
 	Seek(id int32, prefix []byte, f func(k, v []byte))
 	StoreAsBlock(block *block.Block, buf *io.BufBinWriter) error
@@ -359,33 +359,19 @@ func (dao *Simple) PutStateRoot(r *state.MPTRootState) error {
 }
 
 // GetStorageItem returns StorageItem if it exists in the given store.
-func (dao *Simple) GetStorageItem(id int32, key []byte) *state.StorageItem {
+func (dao *Simple) GetStorageItem(id int32, key []byte) state.StorageItem {
 	b, err := dao.Store.Get(makeStorageItemKey(id, key))
 	if err != nil {
 		return nil
 	}
-	r := io.NewBinReaderFromBuf(b)
-
-	si := &state.StorageItem{}
-	si.DecodeBinary(r)
-	if r.Err != nil {
-		return nil
-	}
-
-	return si
+	return b
 }
 
 // PutStorageItem puts given StorageItem for given id with given
 // key into the given store.
-func (dao *Simple) PutStorageItem(id int32, key []byte, si *state.StorageItem) error {
+func (dao *Simple) PutStorageItem(id int32, key []byte, si state.StorageItem) error {
 	stKey := makeStorageItemKey(id, key)
-	buf := io.NewBufBinWriter()
-	si.EncodeBinary(buf.BinWriter)
-	if buf.Err != nil {
-		return buf.Err
-	}
-	v := buf.Bytes()
-	return dao.Store.Put(stKey, v)
+	return dao.Store.Put(stKey, si)
 }
 
 // DeleteStorageItem drops storage item for the given id with the
@@ -396,31 +382,22 @@ func (dao *Simple) DeleteStorageItem(id int32, key []byte) error {
 }
 
 // GetStorageItems returns all storage items for a given id.
-func (dao *Simple) GetStorageItems(id int32) (map[string]*state.StorageItem, error) {
+func (dao *Simple) GetStorageItems(id int32) (map[string]state.StorageItem, error) {
 	return dao.GetStorageItemsWithPrefix(id, nil)
 }
 
 // GetStorageItemsWithPrefix returns all storage items with given id for a
 // given scripthash.
-func (dao *Simple) GetStorageItemsWithPrefix(id int32, prefix []byte) (map[string]*state.StorageItem, error) {
-	var siMap = make(map[string]*state.StorageItem)
-	var err error
+func (dao *Simple) GetStorageItemsWithPrefix(id int32, prefix []byte) (map[string]state.StorageItem, error) {
+	var siMap = make(map[string]state.StorageItem)
 
 	saveToMap := func(k, v []byte) {
-		if err != nil {
-			return
-		}
-		r := io.NewBinReaderFromBuf(v)
-		si := &state.StorageItem{}
-		si.DecodeBinary(r)
-		if r.Err != nil {
-			err = r.Err
-			return
-		}
 		// Cut prefix and hash.
 		// Must copy here, #1468.
 		key := make([]byte, len(k))
 		copy(key, k)
+		si := make(state.StorageItem, len(v))
+		copy(si, v)
 		siMap[string(key)] = si
 	}
 	dao.Seek(id, prefix, saveToMap)
diff --git a/pkg/core/dao/dao_test.go b/pkg/core/dao/dao_test.go
index 97b1ddb54..f17117ccc 100644
--- a/pkg/core/dao/dao_test.go
+++ b/pkg/core/dao/dao_test.go
@@ -64,7 +64,7 @@ func TestPutGetStorageItem(t *testing.T) {
 	dao := NewSimple(storage.NewMemoryStore(), netmode.UnitTestNet, false)
 	id := int32(random.Int(0, 1024))
 	key := []byte{0}
-	storageItem := &state.StorageItem{Value: []uint8{}}
+	storageItem := state.StorageItem{}
 	err := dao.PutStorageItem(id, key, storageItem)
 	require.NoError(t, err)
 	gotStorageItem := dao.GetStorageItem(id, key)
@@ -75,7 +75,7 @@ func TestDeleteStorageItem(t *testing.T) {
 	dao := NewSimple(storage.NewMemoryStore(), netmode.UnitTestNet, false)
 	id := int32(random.Int(0, 1024))
 	key := []byte{0}
-	storageItem := &state.StorageItem{Value: []uint8{}}
+	storageItem := state.StorageItem{}
 	err := dao.PutStorageItem(id, key, storageItem)
 	require.NoError(t, err)
 	err = dao.DeleteStorageItem(id, key)
diff --git a/pkg/core/interop/interopnames/names.go b/pkg/core/interop/interopnames/names.go
index c15dba958..d342284f1 100644
--- a/pkg/core/interop/interopnames/names.go
+++ b/pkg/core/interop/interopnames/names.go
@@ -46,7 +46,6 @@ const (
 	SystemStorageGetContext                  = "System.Storage.GetContext"
 	SystemStorageGetReadOnlyContext          = "System.Storage.GetReadOnlyContext"
 	SystemStoragePut                         = "System.Storage.Put"
-	SystemStoragePutEx                       = "System.Storage.PutEx"
 	SystemStorageAsReadOnly                  = "System.Storage.AsReadOnly"
 	NeoCryptoVerifyWithECDsaSecp256r1        = "Neo.Crypto.VerifyWithECDsaSecp256r1"
 	NeoCryptoVerifyWithECDsaSecp256k1        = "Neo.Crypto.VerifyWithECDsaSecp256k1"
@@ -101,7 +100,6 @@ var names = []string{
 	SystemStorageGetContext,
 	SystemStorageGetReadOnlyContext,
 	SystemStoragePut,
-	SystemStoragePutEx,
 	SystemStorageAsReadOnly,
 	NeoCryptoVerifyWithECDsaSecp256r1,
 	NeoCryptoVerifyWithECDsaSecp256k1,
diff --git a/pkg/core/interop_neo.go b/pkg/core/interop_neo.go
index 98671e6ef..39220a0ee 100644
--- a/pkg/core/interop_neo.go
+++ b/pkg/core/interop_neo.go
@@ -49,7 +49,7 @@ func storageFind(ic *interop.Context) error {
 
 	filteredMap := stackitem.NewMap()
 	for k, v := range siMap {
-		filteredMap.Add(stackitem.NewByteArray(append(prefix, []byte(k)...)), stackitem.NewByteArray(v.Value))
+		filteredMap.Add(stackitem.NewByteArray(append(prefix, []byte(k)...)), stackitem.NewByteArray(v))
 	}
 	sort.Slice(filteredMap.Value().([]stackitem.MapElement), func(i, j int) bool {
 		return bytes.Compare(filteredMap.Value().([]stackitem.MapElement)[i].Key.Value().([]byte),
diff --git a/pkg/core/interop_neo_test.go b/pkg/core/interop_neo_test.go
index 613dae823..8d2976960 100644
--- a/pkg/core/interop_neo_test.go
+++ b/pkg/core/interop_neo_test.go
@@ -51,31 +51,15 @@ func TestStorageFind(t *testing.T) {
 
 	skeys := [][]byte{{0x01, 0x02}, {0x02, 0x01}, {0x01, 0x01},
 		{0x04, 0x00}, {0x05, 0x00}, {0x06}, {0x07}, {0x08}}
-	items := []*state.StorageItem{
-		{
-			Value: []byte{0x01, 0x02, 0x03, 0x04},
-		},
-		{
-			Value: []byte{0x04, 0x03, 0x02, 0x01},
-		},
-		{
-			Value: []byte{0x03, 0x04, 0x05, 0x06},
-		},
-		{
-			Value: []byte{byte(stackitem.ByteArrayT), 2, 0xCA, 0xFE},
-		},
-		{
-			Value: []byte{0xFF, 0xFF},
-		},
-		{
-			Value: rawArr,
-		},
-		{
-			Value: rawArr0,
-		},
-		{
-			Value: rawArr1,
-		},
+	items := []state.StorageItem{
+		[]byte{0x01, 0x02, 0x03, 0x04},
+		[]byte{0x04, 0x03, 0x02, 0x01},
+		[]byte{0x03, 0x04, 0x05, 0x06},
+		[]byte{byte(stackitem.ByteArrayT), 2, 0xCA, 0xFE},
+		[]byte{0xFF, 0xFF},
+		rawArr,
+		rawArr0,
+		rawArr1,
 	}
 
 	require.NoError(t, chain.contracts.Management.PutContractState(chain.dao, contractState))
@@ -121,11 +105,11 @@ func TestStorageFind(t *testing.T) {
 		testFind(t, 0x01, istorage.FindDefault, []stackitem.Item{
 			stackitem.NewStruct([]stackitem.Item{
 				stackitem.NewByteArray(skeys[2]),
-				stackitem.NewByteArray(items[2].Value),
+				stackitem.NewByteArray(items[2]),
 			}),
 			stackitem.NewStruct([]stackitem.Item{
 				stackitem.NewByteArray(skeys[0]),
-				stackitem.NewByteArray(items[0].Value),
+				stackitem.NewByteArray(items[0]),
 			}),
 		})
 	})
@@ -144,13 +128,13 @@ func TestStorageFind(t *testing.T) {
 	})
 	t.Run("values only", func(t *testing.T) {
 		testFind(t, 0x01, istorage.FindValuesOnly, []stackitem.Item{
-			stackitem.NewByteArray(items[2].Value),
-			stackitem.NewByteArray(items[0].Value),
+			stackitem.NewByteArray(items[2]),
+			stackitem.NewByteArray(items[0]),
 		})
 	})
 	t.Run("deserialize values", func(t *testing.T) {
 		testFind(t, 0x04, istorage.FindValuesOnly|istorage.FindDeserialize, []stackitem.Item{
-			stackitem.NewByteArray(items[3].Value[2:]),
+			stackitem.NewByteArray(items[3][2:]),
 		})
 		t.Run("invalid", func(t *testing.T) {
 			v.Estack().PushVal(istorage.FindDeserialize)
diff --git a/pkg/core/interop_system.go b/pkg/core/interop_system.go
index 11f58482e..bfd04fed0 100644
--- a/pkg/core/interop_system.go
+++ b/pkg/core/interop_system.go
@@ -73,10 +73,6 @@ func storageDelete(ic *interop.Context) error {
 	}
 	ic.VM.AddGas(ic.Chain.GetPolicer().GetStoragePrice())
 	key := ic.VM.Estack().Pop().Bytes()
-	si := ic.DAO.GetStorageItem(stc.ID, key)
-	if si != nil && si.IsConst {
-		return errors.New("storage item is constant")
-	}
 	return ic.DAO.DeleteStorageItem(stc.ID, key)
 }
 
@@ -89,8 +85,8 @@ func storageGet(ic *interop.Context) error {
 	}
 	key := ic.VM.Estack().Pop().Bytes()
 	si := ic.DAO.GetStorageItem(stc.ID, key)
-	if si != nil && si.Value != nil {
-		ic.VM.Estack().PushVal(si.Value)
+	if si != nil {
+		ic.VM.Estack().PushVal([]byte(si))
 	} else {
 		ic.VM.Estack().PushVal(stackitem.Null{})
 	}
@@ -122,7 +118,7 @@ func storageGetContextInternal(ic *interop.Context, isReadOnly bool) error {
 	return nil
 }
 
-func putWithContextAndFlags(ic *interop.Context, stc *StorageContext, key []byte, value []byte, isConst bool) error {
+func putWithContext(ic *interop.Context, stc *StorageContext, key []byte, value []byte) error {
 	if len(key) > MaxStorageKeyLen {
 		return errors.New("key is too big")
 	}
@@ -133,30 +129,25 @@ func putWithContextAndFlags(ic *interop.Context, stc *StorageContext, key []byte
 		return errors.New("StorageContext is read only")
 	}
 	si := ic.DAO.GetStorageItem(stc.ID, key)
-	if si != nil && si.IsConst {
-		return errors.New("storage item exists and is read-only")
-	}
-	sizeInc := 1
+	sizeInc := len(value)
 	if si == nil {
-		si = &state.StorageItem{}
+		si = state.StorageItem{}
 		sizeInc = len(key) + len(value)
 	} else if len(value) != 0 {
-		if len(value) <= len(si.Value) {
+		if len(value) <= len(si) {
 			sizeInc = (len(value)-1)/4 + 1
-		} else {
-			sizeInc = (len(si.Value)-1)/4 + 1 + len(value) - len(si.Value)
+		} else if len(si) != 0 {
+			sizeInc = (len(si)-1)/4 + 1 + len(value) - len(si)
 		}
 	}
 	if !ic.VM.AddGas(int64(sizeInc) * ic.Chain.GetPolicer().GetStoragePrice()) {
 		return errGasLimitExceeded
 	}
-	si.Value = value
-	si.IsConst = isConst
-	return ic.DAO.PutStorageItem(stc.ID, key, si)
+	return ic.DAO.PutStorageItem(stc.ID, key, value)
 }
 
-// storagePutInternal is a unified implementation of storagePut and storagePutEx.
-func storagePutInternal(ic *interop.Context, getFlag bool) error {
+// storagePut puts key-value pair into the storage.
+func storagePut(ic *interop.Context) error {
 	stcInterface := ic.VM.Estack().Pop().Value()
 	stc, ok := stcInterface.(*StorageContext)
 	if !ok {
@@ -164,21 +155,7 @@ func storagePutInternal(ic *interop.Context, getFlag bool) error {
 	}
 	key := ic.VM.Estack().Pop().Bytes()
 	value := ic.VM.Estack().Pop().Bytes()
-	var flag int
-	if getFlag {
-		flag = int(ic.VM.Estack().Pop().BigInt().Int64())
-	}
-	return putWithContextAndFlags(ic, stc, key, value, int(Constant)&flag != 0)
-}
-
-// storagePut puts key-value pair into the storage.
-func storagePut(ic *interop.Context) error {
-	return storagePutInternal(ic, false)
-}
-
-// storagePutEx puts key-value pair with given flags into the storage.
-func storagePutEx(ic *interop.Context) error {
-	return storagePutInternal(ic, true)
+	return putWithContext(ic, stc, key, value)
 }
 
 // storageContextAsReadOnly sets given context to read-only mode.
diff --git a/pkg/core/interop_system_test.go b/pkg/core/interop_system_test.go
index ff9e936df..ff2d090f8 100644
--- a/pkg/core/interop_system_test.go
+++ b/pkg/core/interop_system_test.go
@@ -277,21 +277,6 @@ func TestStoragePut(t *testing.T) {
 			initVM(t, []byte{1}, make([]byte, MaxStorageValueLen+1), -1)
 			require.Error(t, storagePut(ic))
 		})
-		t.Run("item exists and is const", func(t *testing.T) {
-			v := ic.SpawnVM()
-			v.LoadScript(cs.NEF.Script)
-			v.GasLimit = -1
-			v.Estack().PushVal(1)
-			v.Estack().PushVal("value")
-			v.Estack().PushVal("key")
-			require.NoError(t, storageGetContext(ic))
-			require.NoError(t, storagePutEx(ic))
-
-			v.Estack().PushVal("new")
-			v.Estack().PushVal("key")
-			require.NoError(t, storageGetContext(ic))
-			require.Error(t, storagePut(ic))
-		})
 	})
 }
 
@@ -301,16 +286,14 @@ func TestStorageDelete(t *testing.T) {
 	require.NoError(t, bc.contracts.Management.PutContractState(ic.DAO, cs))
 	v.LoadScriptWithHash(cs.NEF.Script, cs.Hash, callflag.All)
 	put := func(key, value string, flag int) {
-		v.Estack().PushVal(flag)
 		v.Estack().PushVal(value)
 		v.Estack().PushVal(key)
 		require.NoError(t, storageGetContext(ic))
-		require.NoError(t, storagePutEx(ic))
+		require.NoError(t, storagePut(ic))
 	}
 	put("key1", "value1", 0)
 	put("key2", "value2", 0)
 	put("key3", "value3", 0)
-	put("key4", "value4", 1)
 
 	t.Run("good", func(t *testing.T) {
 		v.Estack().PushVal("key1")
@@ -328,11 +311,6 @@ func TestStorageDelete(t *testing.T) {
 		require.NoError(t, storageContextAsReadOnly(ic))
 		require.Error(t, storageDelete(ic))
 	})
-	t.Run("constant item", func(t *testing.T) {
-		v.Estack().PushVal("key4")
-		require.NoError(t, storageGetContext(ic))
-		require.Error(t, storageDelete(ic))
-	})
 }
 
 // getTestContractState returns 2 contracts second of which is allowed to call the first.
diff --git a/pkg/core/interops.go b/pkg/core/interops.go
index 750a21ba5..9b961ccff 100644
--- a/pkg/core/interops.go
+++ b/pkg/core/interops.go
@@ -82,8 +82,6 @@ var systemInterops = []interop.Function{
 		RequiredFlags: callflag.ReadStates},
 	{Name: interopnames.SystemStoragePut, Func: storagePut, Price: 0, RequiredFlags: callflag.WriteStates,
 		ParamCount: 3}, // These don't have static price in C# code.
-	{Name: interopnames.SystemStoragePutEx, Func: storagePutEx, Price: 0, RequiredFlags: callflag.WriteStates,
-		ParamCount: 4},
 	{Name: interopnames.SystemStorageAsReadOnly, Func: storageContextAsReadOnly, Price: 1 << 4,
 		RequiredFlags: callflag.ReadStates, ParamCount: 1},
 }
diff --git a/pkg/core/interops_test.go b/pkg/core/interops_test.go
index 8f793bd5c..efed8f7cd 100644
--- a/pkg/core/interops_test.go
+++ b/pkg/core/interops_test.go
@@ -39,7 +39,6 @@ func TestUnexpectedNonInterops(t *testing.T) {
 		storageFind,
 		storageGet,
 		storagePut,
-		storagePutEx,
 	}
 	for _, f := range funcs {
 		for k, v := range vals {
diff --git a/pkg/core/native/designate.go b/pkg/core/native/designate.go
index 385faaee3..c7d225861 100644
--- a/pkg/core/native/designate.go
+++ b/pkg/core/native/designate.go
@@ -257,7 +257,7 @@ func (s *Designate) GetDesignatedByRole(d dao.DAO, r Role, index uint32) (keys.P
 	}
 	var ns NodeList
 	var bestIndex uint32
-	var resSi *state.StorageItem
+	var resSi state.StorageItem
 	for k, si := range kvs {
 		if len(k) < 4 {
 			continue
@@ -269,7 +269,7 @@ func (s *Designate) GetDesignatedByRole(d dao.DAO, r Role, index uint32) (keys.P
 		}
 	}
 	if resSi != nil {
-		reader := io.NewBinReaderFromBuf(resSi.Value)
+		reader := io.NewBinReaderFromBuf(resSi)
 		ns.DecodeBinary(reader)
 		if reader.Err != nil {
 			return nil, 0, reader.Err
@@ -324,8 +324,7 @@ func (s *Designate) DesignateAsRole(ic *interop.Context, r Role, pubs keys.Publi
 	}
 	sort.Sort(pubs)
 	s.rolesChangedFlag.Store(true)
-	si = &state.StorageItem{Value: NodeList(pubs).Bytes()}
-	return ic.DAO.PutStorageItem(s.ID, key, si)
+	return ic.DAO.PutStorageItem(s.ID, key, NodeList(pubs).Bytes())
 }
 
 func (s *Designate) getRole(item stackitem.Item) (Role, bool) {
diff --git a/pkg/core/native/management.go b/pkg/core/native/management.go
index eb4582df2..2e74518e8 100644
--- a/pkg/core/native/management.go
+++ b/pkg/core/native/management.go
@@ -480,16 +480,8 @@ func (m *Management) InitializeCache(d dao.DAO) error {
 
 	var initErr error
 	d.Seek(m.ID, []byte{prefixContract}, func(_, v []byte) {
-		var r = io.NewBinReaderFromBuf(v)
-		var si state.StorageItem
-		si.DecodeBinary(r)
-		if r.Err != nil {
-			initErr = r.Err
-			return
-		}
-
 		var cs state.Contract
-		r = io.NewBinReaderFromBuf(si.Value)
+		r := io.NewBinReaderFromBuf(v)
 		cs.DecodeBinary(r)
 		if r.Err != nil {
 			initErr = r.Err
@@ -546,10 +538,10 @@ func (m *Management) getNextContractID(d dao.DAO) (int32, error) {
 		return 0, errors.New("nextAvailableID is not initialized")
 
 	}
-	id := bigint.FromBytes(si.Value)
+	id := bigint.FromBytes(si)
 	ret := int32(id.Int64())
 	id.Add(id, intOne)
-	si.Value = bigint.ToPreallocatedBytes(id, si.Value)
+	si = bigint.ToPreallocatedBytes(id, si)
 	return ret, d.PutStorageItem(m.ID, keyNextAvailableID, si)
 }
 
diff --git a/pkg/core/native/management_test.go b/pkg/core/native/management_test.go
index 05a9894c1..61002accf 100644
--- a/pkg/core/native/management_test.go
+++ b/pkg/core/native/management_test.go
@@ -79,7 +79,7 @@ func TestManagement_Initialize(t *testing.T) {
 	t.Run("invalid contract state", func(t *testing.T) {
 		d := dao.NewSimple(storage.NewMemoryStore(), netmode.UnitTestNet, false)
 		mgmt := newManagement()
-		require.NoError(t, d.PutStorageItem(mgmt.ID, []byte{prefixContract}, &state.StorageItem{Value: []byte{0xFF}}))
+		require.NoError(t, d.PutStorageItem(mgmt.ID, []byte{prefixContract}, state.StorageItem{0xFF}))
 		require.Error(t, mgmt.InitializeCache(d))
 	})
 }
diff --git a/pkg/core/native/name_service.go b/pkg/core/native/name_service.go
index ab724eb7c..23d263156 100644
--- a/pkg/core/native/name_service.go
+++ b/pkg/core/native/name_service.go
@@ -259,8 +259,7 @@ func (n *NameService) setPrice(ic *interop.Context, args []stackitem.Item) stack
 	}
 
 	n.checkCommittee(ic)
-	si := &state.StorageItem{Value: bigint.ToBytes(price)}
-	err := ic.DAO.PutStorageItem(n.ID, []byte{prefixDomainPrice}, si)
+	err := ic.DAO.PutStorageItem(n.ID, []byte{prefixDomainPrice}, bigint.ToBytes(price))
 	if err != nil {
 		panic(err)
 	}
@@ -273,7 +272,7 @@ func (n *NameService) getPrice(ic *interop.Context, _ []stackitem.Item) stackite
 
 func (n *NameService) getPriceInternal(d dao.DAO) *big.Int {
 	si := d.GetStorageItem(n.ID, []byte{prefixDomainPrice})
-	return bigint.FromBytes(si.Value)
+	return bigint.FromBytes(si)
 }
 
 func (n *NameService) parseName(item stackitem.Item) (string, []string, []byte) {
@@ -337,7 +336,7 @@ func (n *NameService) register(ic *interop.Context, args []stackitem.Item) stack
 	n.mint(ic, token)
 	err := ic.DAO.PutStorageItem(n.ID,
 		makeExpirationKey(token.Expiration, token.ID()),
-		&state.StorageItem{Value: []byte{0}})
+		state.StorageItem{0})
 	if err != nil {
 		panic(err)
 	}
@@ -367,8 +366,7 @@ func (n *NameService) renew(ic *interop.Context, args []stackitem.Item) stackite
 	}
 
 	binary.BigEndian.PutUint32(key[1:], token.Expiration)
-	si := &state.StorageItem{Value: []byte{0}}
-	err = ic.DAO.PutStorageItem(n.ID, key, si)
+	err = ic.DAO.PutStorageItem(n.ID, key, state.StorageItem{0})
 	if err != nil {
 		panic(err)
 	}
@@ -441,7 +439,7 @@ func (n *NameService) setRecord(ic *interop.Context, args []stackitem.Item) stac
 		panic("not witnessed by admin")
 	}
 	key := makeRecordKey(domain, name, rt)
-	si := &state.StorageItem{Value: []byte(data)}
+	si := state.StorageItem(data)
 	if err := ic.DAO.PutStorageItem(n.ID, key, si); err != nil {
 		panic(err)
 	}
@@ -478,7 +476,7 @@ func (n *NameService) getRecord(ic *interop.Context, args []stackitem.Item) stac
 	if si == nil {
 		return stackitem.Null{}
 	}
-	return stackitem.NewByteArray(si.Value)
+	return stackitem.NewByteArray(si)
 }
 
 func (n *NameService) deleteRecord(ic *interop.Context, args []stackitem.Item) stackitem.Item {
@@ -535,13 +533,7 @@ func (n *NameService) getRecordsInternal(d dao.DAO, name string) map[RecordType]
 	res := make(map[RecordType]string)
 	d.Seek(n.ID, key, func(k, v []byte) {
 		rt := RecordType(k[len(k)-1])
-		var si state.StorageItem
-		r := io.NewBinReaderFromBuf(v)
-		si.DecodeBinary(r)
-		if r.Err != nil {
-			panic(r.Err)
-		}
-		res[rt] = string(si.Value)
+		res[rt] = string(v)
 	})
 	return res
 }
diff --git a/pkg/core/native/native_gas.go b/pkg/core/native/native_gas.go
index 719706eb1..30e52f704 100644
--- a/pkg/core/native/native_gas.go
+++ b/pkg/core/native/native_gas.go
@@ -41,7 +41,7 @@ func newGAS() *GAS {
 }
 
 func (g *GAS) increaseBalance(_ *interop.Context, _ util.Uint160, si *state.StorageItem, amount *big.Int) error {
-	acc, err := state.NEP17BalanceStateFromBytes(si.Value)
+	acc, err := state.NEP17BalanceStateFromBytes(*si)
 	if err != nil {
 		return err
 	}
@@ -52,9 +52,9 @@ func (g *GAS) increaseBalance(_ *interop.Context, _ util.Uint160, si *state.Stor
 	}
 	acc.Balance.Add(&acc.Balance, amount)
 	if acc.Balance.Sign() != 0 {
-		si.Value = acc.Bytes()
+		*si = acc.Bytes()
 	} else {
-		si.Value = nil
+		*si = nil
 	}
 	return nil
 }
diff --git a/pkg/core/native/native_neo.go b/pkg/core/native/native_neo.go
index 24ec29dd9..17b35acdc 100644
--- a/pkg/core/native/native_neo.go
+++ b/pkg/core/native/native_neo.go
@@ -20,7 +20,6 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/bigint"
-	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract/manifest"
@@ -172,7 +171,7 @@ func (n *NEO) Initialize(ic *interop.Context) error {
 		return err
 	}
 
-	err = ic.DAO.PutStorageItem(n.ID, prefixCommittee, &state.StorageItem{Value: cvs.Bytes()})
+	err = ic.DAO.PutStorageItem(n.ID, prefixCommittee, cvs.Bytes())
 	if err != nil {
 		return err
 	}
@@ -192,7 +191,7 @@ func (n *NEO) Initialize(ic *interop.Context) error {
 	gr := &gasRecord{{Index: index, GASPerBlock: *value}}
 	n.gasPerBlock.Store(*gr)
 	n.gasPerBlockChanged.Store(false)
-	err = ic.DAO.PutStorageItem(n.ID, []byte{prefixVotersCount}, &state.StorageItem{Value: []byte{}})
+	err = ic.DAO.PutStorageItem(n.ID, []byte{prefixVotersCount}, state.StorageItem{})
 	if err != nil {
 		return err
 	}
@@ -206,7 +205,7 @@ func (n *NEO) Initialize(ic *interop.Context) error {
 func (n *NEO) InitializeCache(bc blockchainer.Blockchainer, d dao.DAO) error {
 	var committee = keysWithVotes{}
 	si := d.GetStorageItem(n.ID, prefixCommittee)
-	if err := committee.DecodeBytes(si.Value); err != nil {
+	if err := committee.DecodeBytes(si); err != nil {
 		return err
 	}
 	if err := n.updateCache(committee, bc); err != nil {
@@ -244,8 +243,7 @@ func (n *NEO) updateCommittee(ic *interop.Context) error {
 	if !votesChanged {
 		// We need to put in storage anyway, as it affects dumps
 		committee := n.committee.Load().(keysWithVotes)
-		si := &state.StorageItem{Value: committee.Bytes()}
-		return ic.DAO.PutStorageItem(n.ID, prefixCommittee, si)
+		return ic.DAO.PutStorageItem(n.ID, prefixCommittee, committee.Bytes())
 	}
 
 	_, cvs, err := n.computeCommitteeMembers(ic.Chain, ic.DAO)
@@ -256,8 +254,7 @@ func (n *NEO) updateCommittee(ic *interop.Context) error {
 		return err
 	}
 	n.votesChanged.Store(false)
-	si := &state.StorageItem{Value: cvs.Bytes()}
-	return ic.DAO.PutStorageItem(n.ID, prefixCommittee, si)
+	return ic.DAO.PutStorageItem(n.ID, prefixCommittee, cvs.Bytes())
 }
 
 // ShouldUpdateCommittee returns true if committee is updated at block h.
@@ -295,7 +292,6 @@ func (n *NEO) PostPersist(ic *interop.Context) error {
 		voterReward.Div(voterReward, big.NewInt(100))
 
 		var cs = n.committee.Load().(keysWithVotes)
-		var si = new(state.StorageItem)
 		var key = make([]byte, 38)
 		for i := range cs {
 			if cs[i].Votes.Sign() > 0 {
@@ -312,8 +308,7 @@ func (n *NEO) PostPersist(ic *interop.Context) error {
 
 				binary.BigEndian.PutUint32(key[34:], ic.Block.Index+1)
 
-				si.Value = bigint.ToBytes(tmp)
-				if err := ic.DAO.PutStorageItem(n.ID, key, si); err != nil {
+				if err := ic.DAO.PutStorageItem(n.ID, key, bigint.ToBytes(tmp)); err != nil {
 					return err
 				}
 			}
@@ -334,19 +329,13 @@ func (n *NEO) PostPersist(ic *interop.Context) error {
 func (n *NEO) getGASPerVote(d dao.DAO, key []byte, index ...uint32) []big.Int {
 	var max = make([]uint32, len(index))
 	var reward = make([]big.Int, len(index))
-	var si state.StorageItem
 	d.Seek(n.ID, key, func(k, v []byte) {
 		if len(k) == 4 {
 			num := binary.BigEndian.Uint32(k)
 			for i, ind := range index {
 				if max[i] < num && num <= ind {
 					max[i] = num
-					r := io.NewBinReaderFromBuf(v)
-					si.DecodeBinary(r)
-					if r.Err != nil {
-						return
-					}
-					reward[i] = *bigint.FromBytes(si.Value)
+					reward[i] = *bigint.FromBytes(v)
 				}
 			}
 		}
@@ -355,7 +344,7 @@ func (n *NEO) getGASPerVote(d dao.DAO, key []byte, index ...uint32) []big.Int {
 }
 
 func (n *NEO) increaseBalance(ic *interop.Context, h util.Uint160, si *state.StorageItem, amount *big.Int) error {
-	acc, err := state.NEOBalanceStateFromBytes(si.Value)
+	acc, err := state.NEOBalanceStateFromBytes(*si)
 	if err != nil {
 		return err
 	}
@@ -366,7 +355,7 @@ func (n *NEO) increaseBalance(ic *interop.Context, h util.Uint160, si *state.Sto
 		return err
 	}
 	if amount.Sign() == 0 {
-		si.Value = acc.Bytes()
+		*si = acc.Bytes()
 		return nil
 	}
 	if err := n.ModifyAccountVotes(acc, ic.DAO, amount, false); err != nil {
@@ -379,9 +368,9 @@ func (n *NEO) increaseBalance(ic *interop.Context, h util.Uint160, si *state.Sto
 	}
 	acc.Balance.Add(&acc.Balance, amount)
 	if acc.Balance.Sign() != 0 {
-		si.Value = acc.Bytes()
+		*si = acc.Bytes()
 	} else {
-		si.Value = nil
+		*si = nil
 	}
 	return nil
 }
@@ -426,7 +415,7 @@ func (n *NEO) getSortedGASRecordFromDAO(d dao.DAO) (gasRecord, error) {
 	for indexBytes, gasValue := range grMap {
 		gr[i] = gasIndexPair{
 			Index:       binary.BigEndian.Uint32([]byte(indexBytes)),
-			GASPerBlock: *bigint.FromBytes(gasValue.Value),
+			GASPerBlock: *bigint.FromBytes(gasValue),
 		}
 		i++
 	}
@@ -533,7 +522,7 @@ func (n *NEO) CalculateBonus(d dao.DAO, acc util.Uint160, end uint32) (*big.Int,
 	if si == nil {
 		return nil, storage.ErrKeyNotFound
 	}
-	st, err := state.NEOBalanceStateFromBytes(si.Value)
+	st, err := state.NEOBalanceStateFromBytes(si)
 	if err != nil {
 		return nil, err
 	}
@@ -611,15 +600,14 @@ func (n *NEO) registerCandidate(ic *interop.Context, args []stackitem.Item) stac
 func (n *NEO) RegisterCandidateInternal(ic *interop.Context, pub *keys.PublicKey) error {
 	key := makeValidatorKey(pub)
 	si := ic.DAO.GetStorageItem(n.ID, key)
+	var c *candidate
 	if si == nil {
-		c := &candidate{Registered: true}
-		si = &state.StorageItem{Value: c.Bytes()}
+		c = &candidate{Registered: true}
 	} else {
-		c := new(candidate).FromBytes(si.Value)
+		c = new(candidate).FromBytes(si)
 		c.Registered = true
-		si.Value = c.Bytes()
 	}
-	return ic.DAO.PutStorageItem(n.ID, key, si)
+	return ic.DAO.PutStorageItem(n.ID, key, c.Bytes())
 }
 
 func (n *NEO) unregisterCandidate(ic *interop.Context, args []stackitem.Item) stackitem.Item {
@@ -642,14 +630,13 @@ func (n *NEO) UnregisterCandidateInternal(ic *interop.Context, pub *keys.PublicK
 		return nil
 	}
 	n.validators.Store(keys.PublicKeys(nil))
-	c := new(candidate).FromBytes(si.Value)
+	c := new(candidate).FromBytes(si)
 	c.Registered = false
 	ok, err := n.dropCandidateIfZero(ic.DAO, pub, c)
 	if ok {
 		return err
 	}
-	si.Value = c.Bytes()
-	return ic.DAO.PutStorageItem(n.ID, key, si)
+	return ic.DAO.PutStorageItem(n.ID, key, c.Bytes())
 }
 
 func (n *NEO) vote(ic *interop.Context, args []stackitem.Item) stackitem.Item {
@@ -675,7 +662,7 @@ func (n *NEO) VoteInternal(ic *interop.Context, h util.Uint160, pub *keys.Public
 	if si == nil {
 		return errors.New("invalid account")
 	}
-	acc, err := state.NEOBalanceStateFromBytes(si.Value)
+	acc, err := state.NEOBalanceStateFromBytes(si)
 	if err != nil {
 		return err
 	}
@@ -698,8 +685,7 @@ func (n *NEO) VoteInternal(ic *interop.Context, h util.Uint160, pub *keys.Public
 	if err := n.ModifyAccountVotes(acc, ic.DAO, &acc.Balance, true); err != nil {
 		return err
 	}
-	si.Value = acc.Bytes()
-	return ic.DAO.PutStorageItem(n.ID, key, si)
+	return ic.DAO.PutStorageItem(n.ID, key, acc.Bytes())
 }
 
 // ModifyAccountVotes modifies votes of the specified account by value (can be negative).
@@ -712,7 +698,7 @@ func (n *NEO) ModifyAccountVotes(acc *state.NEOBalanceState, d dao.DAO, value *b
 		if si == nil {
 			return errors.New("invalid validator")
 		}
-		cd := new(candidate).FromBytes(si.Value)
+		cd := new(candidate).FromBytes(si)
 		cd.Votes.Add(&cd.Votes, value)
 		if !isNewVote {
 			ok, err := n.dropCandidateIfZero(d, acc.VoteTo, cd)
@@ -723,8 +709,7 @@ func (n *NEO) ModifyAccountVotes(acc *state.NEOBalanceState, d dao.DAO, value *b
 			return errors.New("validator must be registered")
 		}
 		n.validators.Store(keys.PublicKeys(nil))
-		si.Value = cd.Bytes()
-		return d.PutStorageItem(n.ID, key, si)
+		return d.PutStorageItem(n.ID, key, cd.Bytes())
 	}
 	return nil
 }
@@ -736,7 +721,7 @@ func (n *NEO) getCandidates(d dao.DAO, sortByKey bool) ([]keyWithVotes, error) {
 	}
 	arr := make([]keyWithVotes, 0, len(siMap))
 	for key, si := range siMap {
-		c := new(candidate).FromBytes(si.Value)
+		c := new(candidate).FromBytes(si)
 		if c.Registered {
 			arr = append(arr, keyWithVotes{Key: key, Votes: &c.Votes})
 		}
@@ -817,9 +802,9 @@ func (n *NEO) modifyVoterTurnout(d dao.DAO, amount *big.Int) error {
 	if si == nil {
 		return errors.New("voters count not found")
 	}
-	votersCount := bigint.FromBytes(si.Value)
+	votersCount := bigint.FromBytes(si)
 	votersCount.Add(votersCount, amount)
-	si.Value = bigint.ToBytes(votersCount)
+	si = bigint.ToPreallocatedBytes(votersCount, si)
 	return d.PutStorageItem(n.ID, key, si)
 }
 
@@ -854,7 +839,7 @@ func (n *NEO) computeCommitteeMembers(bc blockchainer.Blockchainer, d dao.DAO) (
 	if si == nil {
 		return nil, nil, errors.New("voters count not found")
 	}
-	votersCount := bigint.FromBytes(si.Value)
+	votersCount := bigint.FromBytes(si)
 	// votersCount / totalSupply must be >= 0.2
 	votersCount.Mul(votersCount, big.NewInt(effectiveVoterTurnout))
 	voterTurnout := votersCount.Div(votersCount, n.getTotalSupply(d))
@@ -926,9 +911,5 @@ func (n *NEO) putGASRecord(dao dao.DAO, index uint32, value *big.Int) error {
 	key := make([]byte, 5)
 	key[0] = prefixGASPerBlock
 	binary.BigEndian.PutUint32(key[1:], index)
-	si := &state.StorageItem{
-		Value:   bigint.ToBytes(value),
-		IsConst: false,
-	}
-	return dao.PutStorageItem(n.ID, key, si)
+	return dao.PutStorageItem(n.ID, key, bigint.ToBytes(value))
 }
diff --git a/pkg/core/native/native_nep17.go b/pkg/core/native/native_nep17.go
index 6cad29c4d..2dd171ac3 100644
--- a/pkg/core/native/native_nep17.go
+++ b/pkg/core/native/native_nep17.go
@@ -100,12 +100,11 @@ func (c *nep17TokenNative) getTotalSupply(d dao.DAO) *big.Int {
 	if si == nil {
 		return big.NewInt(0)
 	}
-	return bigint.FromBytes(si.Value)
+	return bigint.FromBytes(si)
 }
 
 func (c *nep17TokenNative) saveTotalSupply(d dao.DAO, supply *big.Int) error {
-	si := &state.StorageItem{Value: bigint.ToBytes(supply)}
-	return d.PutStorageItem(c.ID, totalSupplyKey, si)
+	return d.PutStorageItem(c.ID, totalSupplyKey, bigint.ToBytes(supply))
 }
 
 func (c *nep17TokenNative) Transfer(ic *interop.Context, args []stackitem.Item) stackitem.Item {
@@ -168,14 +167,14 @@ func (c *nep17TokenNative) updateAccBalance(ic *interop.Context, acc util.Uint16
 		if amount.Sign() <= 0 {
 			return errors.New("insufficient funds")
 		}
-		si = new(state.StorageItem)
+		si = state.StorageItem{}
 	}
 
-	err := c.incBalance(ic, acc, si, amount)
+	err := c.incBalance(ic, acc, &si, amount)
 	if err != nil {
 		return err
 	}
-	if si.Value == nil {
+	if si == nil {
 		err = ic.DAO.DeleteStorageItem(c.ID, key)
 	} else {
 		err = ic.DAO.PutStorageItem(c.ID, key, si)
@@ -253,13 +252,13 @@ func (c *nep17TokenNative) addTokens(ic *interop.Context, h util.Uint160, amount
 	key := makeAccountKey(h)
 	si := ic.DAO.GetStorageItem(c.ID, key)
 	if si == nil {
-		si = new(state.StorageItem)
+		si = state.StorageItem{}
 	}
-	if err := c.incBalance(ic, h, si, amount); err != nil {
+	if err := c.incBalance(ic, h, &si, amount); err != nil {
 		panic(err)
 	}
 	var err error
-	if si.Value == nil {
+	if si == nil {
 		err = ic.DAO.DeleteStorageItem(c.ID, key)
 	} else {
 		err = ic.DAO.PutStorageItem(c.ID, key, si)
diff --git a/pkg/core/native/nonfungible.go b/pkg/core/native/nonfungible.go
index 4883f73c9..5d93392c6 100644
--- a/pkg/core/native/nonfungible.go
+++ b/pkg/core/native/nonfungible.go
@@ -141,12 +141,11 @@ func (n *nonfungible) TotalSupply(d dao.DAO) *big.Int {
 	if si == nil {
 		panic(errors.New("total supply is not initialized"))
 	}
-	return bigint.FromBytes(si.Value)
+	return bigint.FromBytes(si)
 }
 
 func (n *nonfungible) setTotalSupply(d dao.DAO, ts *big.Int) {
-	si := &state.StorageItem{Value: bigint.ToBytes(ts)}
-	err := d.PutStorageItem(n.ID, nftTotalSupplyKey, si)
+	err := d.PutStorageItem(n.ID, nftTotalSupplyKey, bigint.ToBytes(ts))
 	if err != nil {
 		panic(err)
 	}
@@ -222,7 +221,7 @@ func (n *nonfungible) tokens(ic *interop.Context, args []stackitem.Item) stackit
 	}
 	filteredMap := stackitem.NewMap()
 	for k, v := range siMap {
-		filteredMap.Add(stackitem.NewByteArray(append(prefix, []byte(k)...)), stackitem.NewByteArray(v.Value))
+		filteredMap.Add(stackitem.NewByteArray(append(prefix, []byte(k)...)), stackitem.NewByteArray(v))
 	}
 	sort.Slice(filteredMap.Value().([]stackitem.MapElement), func(i, j int) bool {
 		return bytes.Compare(filteredMap.Value().([]stackitem.MapElement)[i].Key.Value().([]byte),
diff --git a/pkg/core/native/oracle.go b/pkg/core/native/oracle.go
index cd6fce0ad..e6029cc62 100644
--- a/pkg/core/native/oracle.go
+++ b/pkg/core/native/oracle.go
@@ -166,8 +166,7 @@ func (o *Oracle) PostPersist(ic *interop.Context) error {
 		if len(*idList) == 0 {
 			err = ic.DAO.DeleteStorageItem(o.ID, idKey)
 		} else {
-			si := &state.StorageItem{Value: idList.Bytes()}
-			err = ic.DAO.PutStorageItem(o.ID, idKey, si)
+			err = ic.DAO.PutStorageItem(o.ID, idKey, idList.Bytes())
 		}
 		if err != nil {
 			return err
@@ -303,10 +302,10 @@ func (o *Oracle) RequestInternal(ic *interop.Context, url string, filter *string
 	callingHash := ic.VM.GetCallingScriptHash()
 	o.GAS.mint(ic, o.Hash, gas, false)
 	si := ic.DAO.GetStorageItem(o.ID, prefixRequestID)
-	itemID := bigint.FromBytes(si.Value)
+	itemID := bigint.FromBytes(si)
 	id := itemID.Uint64()
 	itemID.Add(itemID, intOne)
-	si.Value = bigint.ToPreallocatedBytes(itemID, si.Value)
+	si = bigint.ToPreallocatedBytes(itemID, si)
 	if err := ic.DAO.PutStorageItem(o.ID, prefixRequestID, si); err != nil {
 		return err
 	}
@@ -357,9 +356,8 @@ func (o *Oracle) RequestInternal(ic *interop.Context, url string, filter *string
 
 // PutRequestInternal puts oracle request with the specified id to d.
 func (o *Oracle) PutRequestInternal(id uint64, req *state.OracleRequest, d dao.DAO) error {
-	reqItem := &state.StorageItem{Value: req.Bytes()}
 	reqKey := makeRequestKey(id)
-	if err := d.PutStorageItem(o.ID, reqKey, reqItem); err != nil {
+	if err := d.PutStorageItem(o.ID, reqKey, req.Bytes()); err != nil {
 		return err
 	}
 	o.newRequests[id] = req
@@ -374,8 +372,7 @@ func (o *Oracle) PutRequestInternal(id uint64, req *state.OracleRequest, d dao.D
 		return fmt.Errorf("there are too many pending requests for %s url", req.URL)
 	}
 	*lst = append(*lst, id)
-	si := &state.StorageItem{Value: lst.Bytes()}
-	return d.PutStorageItem(o.ID, key, si)
+	return d.PutStorageItem(o.ID, key, lst.Bytes())
 }
 
 // GetScriptHash returns script hash or oracle nodes.
@@ -429,7 +426,7 @@ func (o *Oracle) getRequests(d dao.DAO) (map[uint64]*state.OracleRequest, error)
 		if len(k) != 8 {
 			return nil, errors.New("invalid request ID")
 		}
-		r := io.NewBinReaderFromBuf(si.Value)
+		r := io.NewBinReaderFromBuf(si)
 		req := new(state.OracleRequest)
 		req.DecodeBinary(r)
 		if r.Err != nil {
diff --git a/pkg/core/native/policy.go b/pkg/core/native/policy.go
index 67b00c4bd..368d4926c 100644
--- a/pkg/core/native/policy.go
+++ b/pkg/core/native/policy.go
@@ -325,9 +325,7 @@ func (p *Policy) blockAccount(ic *interop.Context, args []stackitem.Item) stacki
 	key := append([]byte{blockedAccountPrefix}, hash.BytesBE()...)
 	p.lock.Lock()
 	defer p.lock.Unlock()
-	err := ic.DAO.PutStorageItem(p.ID, key, &state.StorageItem{
-		Value: []byte{},
-	})
+	err := ic.DAO.PutStorageItem(p.ID, key, state.StorageItem{})
 	if err != nil {
 		panic(err)
 	}
diff --git a/pkg/core/native/util.go b/pkg/core/native/util.go
index 30d5e9e8a..af7ffd6e7 100644
--- a/pkg/core/native/util.go
+++ b/pkg/core/native/util.go
@@ -22,7 +22,7 @@ func getSerializableFromDAO(id int32, d dao.DAO, key []byte, item io.Serializabl
 	if si == nil {
 		return storage.ErrKeyNotFound
 	}
-	r := io.NewBinReaderFromBuf(si.Value)
+	r := io.NewBinReaderFromBuf(si)
 	item.DecodeBinary(r)
 	return r.Err
 }
@@ -33,9 +33,7 @@ func putSerializableToDAO(id int32, d dao.DAO, key []byte, item io.Serializable)
 	if w.Err != nil {
 		return w.Err
 	}
-	return d.PutStorageItem(id, key, &state.StorageItem{
-		Value: w.Bytes(),
-	})
+	return d.PutStorageItem(id, key, w.Bytes())
 }
 
 func getInt64WithKey(id int32, d dao.DAO, key []byte, defaultValue int64) int64 {
@@ -43,14 +41,12 @@ func getInt64WithKey(id int32, d dao.DAO, key []byte, defaultValue int64) int64
 	if si == nil {
 		return defaultValue
 	}
-	return int64(binary.LittleEndian.Uint64(si.Value))
+	return int64(binary.LittleEndian.Uint64(si))
 }
 
 func setInt64WithKey(id int32, dao dao.DAO, key []byte, value int64) error {
-	si := &state.StorageItem{
-		Value: make([]byte, 8),
-	}
-	binary.LittleEndian.PutUint64(si.Value, uint64(value))
+	si := make(state.StorageItem, 8)
+	binary.LittleEndian.PutUint64(si, uint64(value))
 	return dao.PutStorageItem(id, key, si)
 }
 
@@ -59,20 +55,17 @@ func getUint32WithKey(id int32, dao dao.DAO, key []byte, defaultValue uint32) ui
 	if si == nil {
 		return defaultValue
 	}
-	return binary.LittleEndian.Uint32(si.Value)
+	return binary.LittleEndian.Uint32(si)
 }
 
 func setUint32WithKey(id int32, dao dao.DAO, key []byte, value uint32) error {
-	si := &state.StorageItem{
-		Value: make([]byte, 4),
-	}
-	binary.LittleEndian.PutUint32(si.Value, value)
+	si := make(state.StorageItem, 4)
+	binary.LittleEndian.PutUint32(si, value)
 	return dao.PutStorageItem(id, key, si)
 }
 
 func setIntWithKey(id int32, dao dao.DAO, key []byte, value int64) error {
-	si := &state.StorageItem{Value: bigint.ToBytes(big.NewInt(value))}
-	return dao.PutStorageItem(id, key, si)
+	return dao.PutStorageItem(id, key, bigint.ToBytes(big.NewInt(value)))
 }
 
 func getIntWithKey(id int32, dao dao.DAO, key []byte) int64 {
@@ -81,7 +74,7 @@ func getIntWithKey(id int32, dao dao.DAO, key []byte) int64 {
 		panic(fmt.Errorf("item with id = %d and key = %s is not initialized", id, hex.EncodeToString(key)))
 
 	}
-	return bigint.FromBytes(si.Value).Int64()
+	return bigint.FromBytes(si).Int64()
 }
 
 // makeUint160Key creates a key from account script hash.
diff --git a/pkg/core/native_management_test.go b/pkg/core/native_management_test.go
index 294a94154..ceaf4b204 100644
--- a/pkg/core/native_management_test.go
+++ b/pkg/core/native_management_test.go
@@ -553,7 +553,7 @@ func TestContractDestroy(t *testing.T) {
 	cs1.Manifest.Permissions = []manifest.Permission{*manifest.NewPermission(manifest.PermissionWildcard)}
 	err := bc.contracts.Management.PutContractState(bc.dao, cs1)
 	require.NoError(t, err)
-	err = bc.dao.PutStorageItem(cs1.ID, []byte{1, 2, 3}, &state.StorageItem{Value: []byte{3, 2, 1}})
+	err = bc.dao.PutStorageItem(cs1.ID, []byte{1, 2, 3}, state.StorageItem{3, 2, 1})
 	require.NoError(t, err)
 	require.NoError(t, bc.dao.UpdateMPT())
 
diff --git a/pkg/core/native_oracle_test.go b/pkg/core/native_oracle_test.go
index d1564451d..16f792c0c 100644
--- a/pkg/core/native_oracle_test.go
+++ b/pkg/core/native_oracle_test.go
@@ -180,7 +180,7 @@ func TestOracle_Request(t *testing.T) {
 
 	si := ic.DAO.GetStorageItem(cs.ID, []byte("lastOracleResponse"))
 	require.NotNil(t, si)
-	item, err := stackitem.DeserializeItem(si.Value)
+	item, err := stackitem.DeserializeItem(si)
 	require.NoError(t, err)
 	arr, ok := item.Value().([]stackitem.Item)
 	require.True(t, ok)
diff --git a/pkg/core/state/storage_item.go b/pkg/core/state/storage_item.go
index 95f1f1c6c..ba9777cf8 100644
--- a/pkg/core/state/storage_item.go
+++ b/pkg/core/state/storage_item.go
@@ -1,23 +1,4 @@
 package state
 
-import (
-	"github.com/nspcc-dev/neo-go/pkg/io"
-)
-
 // StorageItem is the value to be stored with read-only flag.
-type StorageItem struct {
-	Value   []byte
-	IsConst bool
-}
-
-// EncodeBinary implements Serializable interface.
-func (si *StorageItem) EncodeBinary(w *io.BinWriter) {
-	w.WriteVarBytes(si.Value)
-	w.WriteBool(si.IsConst)
-}
-
-// DecodeBinary implements Serializable interface.
-func (si *StorageItem) DecodeBinary(r *io.BinReader) {
-	si.Value = r.ReadVarBytes()
-	si.IsConst = r.ReadBool()
-}
+type StorageItem []byte
diff --git a/pkg/core/state/storage_item_test.go b/pkg/core/state/storage_item_test.go
deleted file mode 100644
index 0da9c2a31..000000000
--- a/pkg/core/state/storage_item_test.go
+++ /dev/null
@@ -1,16 +0,0 @@
-package state
-
-import (
-	"testing"
-
-	"github.com/nspcc-dev/neo-go/internal/testserdes"
-)
-
-func TestEncodeDecodeStorageItem(t *testing.T) {
-	storageItem := &StorageItem{
-		Value:   []byte{},
-		IsConst: false,
-	}
-
-	testserdes.EncodeDecodeBinary(t, storageItem, new(StorageItem))
-}
diff --git a/pkg/encoding/bigint/bigint.go b/pkg/encoding/bigint/bigint.go
index 9b77fae65..ed562821d 100644
--- a/pkg/encoding/bigint/bigint.go
+++ b/pkg/encoding/bigint/bigint.go
@@ -19,6 +19,9 @@ func FromBytes(data []byte) *big.Int {
 	n := new(big.Int)
 	size := len(data)
 	if size == 0 {
+		if data == nil {
+			panic("nil slice provided to `FromBytes`")
+		}
 		return big.NewInt(0)
 	}
 
diff --git a/pkg/interop/storage/storage.go b/pkg/interop/storage/storage.go
index c9775ebfa..08392de20 100644
--- a/pkg/interop/storage/storage.go
+++ b/pkg/interop/storage/storage.go
@@ -38,16 +38,6 @@ const (
 	PickField1 FindFlags = 1 << 5
 )
 
-// PutFlags represents flag of `PutEx` syscall.
-type PutFlags byte
-
-const (
-	// PutDefault is a storage flag for non-constant items.
-	PutDefault PutFlags = 0
-	// PutConstant is a storage flag for constant items.
-	PutConstant PutFlags = 0x01
-)
-
 // ConvertContextToReadOnly returns new context from the given one, but with
 // writing capability turned off, so that you could only invoke Get and Find
 // using this new Context. If Context is already read-only this function is a
@@ -79,15 +69,6 @@ func Put(ctx Context, key interface{}, value interface{}) {
 	neogointernal.Syscall3NoReturn("System.Storage.Put", ctx, key, value)
 }
 
-// PutEx is an advanced version of Put which saves given value with given key
-// and given ReadOnly flag in the storage using given Context. `flag` argument
-// can either be odd for constant storage items or even for variable storage items.
-// Refer to Put function description for details on how to pass the remaining
-// arguments. This function uses `System.Storage.PutEx` syscall.
-func PutEx(ctx Context, key interface{}, value interface{}, flag PutFlags) {
-	neogointernal.Syscall4NoReturn("System.Storage.PutEx", ctx, key, value, flag)
-}
-
 // Get retrieves value stored for the given key using given Context. See Put
 // documentation on possible key and value types. If the value is not present in
 // the database it returns nil. This function uses `System.Storage.Get` syscall.
diff --git a/pkg/rpc/server/server.go b/pkg/rpc/server/server.go
index db9878fb4..db22543d7 100644
--- a/pkg/rpc/server/server.go
+++ b/pkg/rpc/server/server.go
@@ -862,13 +862,7 @@ func (s *Server) verifyProof(ps request.Params) (interface{}, *response.Error) {
 	vp := new(result.VerifyProof)
 	val, ok := mpt.VerifyProof(root, p.Key, p.Proof)
 	if ok {
-		var si state.StorageItem
-		r := io.NewBinReaderFromBuf(val)
-		si.DecodeBinary(r)
-		if r.Err != nil {
-			return nil, response.NewInternalServerError("invalid item in trie", r.Err)
-		}
-		vp.Value = si.Value
+		vp.Value = val
 	}
 	return vp, nil
 }
@@ -927,7 +921,7 @@ func (s *Server) getStorage(ps request.Params) (interface{}, *response.Error) {
 		return "", nil
 	}
 
-	return item.Value, nil
+	return []byte(item), nil
 }
 
 func (s *Server) getrawtransaction(reqParams request.Params) (interface{}, *response.Error) {