diff --git a/pkg/compiler/panic_test.go b/pkg/compiler/panic_test.go
index 8504f72d4..646bca04e 100644
--- a/pkg/compiler/panic_test.go
+++ b/pkg/compiler/panic_test.go
@@ -62,7 +62,7 @@ func getLogHandler(logs *[]string) vm.SyscallHandler {
 			return errors.New("syscall not found")
 		}
 
-		msg := string(v.Estack().Pop().Bytes())
+		msg := v.Estack().Pop().String()
 		*logs = append(*logs, msg)
 		return nil
 	}
diff --git a/pkg/compiler/vm_test.go b/pkg/compiler/vm_test.go
index 7456eedc4..ce862a93e 100644
--- a/pkg/compiler/vm_test.go
+++ b/pkg/compiler/vm_test.go
@@ -129,7 +129,7 @@ func (s *storagePlugin) syscallHandler(v *vm.VM, id uint32) error {
 }
 
 func (s *storagePlugin) Notify(v *vm.VM) error {
-	name := string(v.Estack().Pop().Bytes())
+	name := v.Estack().Pop().String()
 	item := stackitem.NewArray(v.Estack().Pop().Array())
 	s.events = append(s.events, state.NotificationEvent{
 		Name: name,
diff --git a/pkg/core/interop_neo.go b/pkg/core/interop_neo.go
index 5f5ffb943..5fa5d3067 100644
--- a/pkg/core/interop_neo.go
+++ b/pkg/core/interop_neo.go
@@ -205,7 +205,7 @@ func runtimeEncode(_ *interop.Context, v *vm.VM) error {
 
 // runtimeDecode decodes top stack item from base64 string to byte array.
 func runtimeDecode(_ *interop.Context, v *vm.VM) error {
-	src := string(v.Estack().Pop().Bytes())
+	src := v.Estack().Pop().String()
 	result, err := base64.StdEncoding.DecodeString(src)
 	if err != nil {
 		return err
diff --git a/pkg/core/interop_system.go b/pkg/core/interop_system.go
index b7aaa116a..44d9279d3 100644
--- a/pkg/core/interop_system.go
+++ b/pkg/core/interop_system.go
@@ -7,7 +7,6 @@ import (
 	"math"
 	"math/big"
 	"strings"
-	"unicode/utf8"
 
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
 	"github.com/nspcc-dev/neo-go/pkg/core/blockchainer"
@@ -265,13 +264,10 @@ func runtimeGetTrigger(ic *interop.Context, v *vm.VM) error {
 // runtimeNotify should pass stack item to the notify plugin to handle it, but
 // in neo-go the only meaningful thing to do here is to log.
 func runtimeNotify(ic *interop.Context, v *vm.VM) error {
-	name := v.Estack().Pop().Bytes()
+	name := v.Estack().Pop().String()
 	if len(name) > MaxEventNameLen {
 		return fmt.Errorf("event name must be less than %d", MaxEventNameLen)
 	}
-	if !utf8.Valid(name) {
-		return errors.New("event name should be UTF8-encoded")
-	}
 	elem := v.Estack().Pop()
 	args := elem.Array()
 	// But it has to be serializable, otherwise we either have some broken
@@ -285,7 +281,7 @@ func runtimeNotify(ic *interop.Context, v *vm.VM) error {
 	}
 	ne := state.NotificationEvent{
 		ScriptHash: v.GetCurrentScriptHash(),
-		Name:       string(name),
+		Name:       name,
 		Item:       stackitem.NewArray(args),
 	}
 	ic.Notifications = append(ic.Notifications, ne)
@@ -294,13 +290,10 @@ func runtimeNotify(ic *interop.Context, v *vm.VM) error {
 
 // runtimeLog logs the message passed.
 func runtimeLog(ic *interop.Context, v *vm.VM) error {
-	state := v.Estack().Pop().Bytes()
+	state := v.Estack().Pop().String()
 	if len(state) > MaxNotificationSize {
 		return fmt.Errorf("message length shouldn't exceed %v", MaxNotificationSize)
 	}
-	if !utf8.Valid(state) {
-		return errors.New("log message should be UTF8-encoded")
-	}
 	msg := fmt.Sprintf("%q", state)
 	ic.Log.Info("runtime log",
 		zap.Stringer("script", v.GetCurrentScriptHash()),
@@ -464,16 +457,16 @@ func storageContextAsReadOnly(ic *interop.Context, v *vm.VM) error {
 // contractCall calls a contract.
 func contractCall(ic *interop.Context, v *vm.VM) error {
 	h := v.Estack().Pop().Bytes()
-	method := v.Estack().Pop().Item()
-	args := v.Estack().Pop().Item()
+	method := v.Estack().Pop().String()
+	args := v.Estack().Pop().Array()
 	return contractCallExInternal(ic, v, h, method, args, smartcontract.All)
 }
 
 // contractCallEx calls a contract with flags.
 func contractCallEx(ic *interop.Context, v *vm.VM) error {
 	h := v.Estack().Pop().Bytes()
-	method := v.Estack().Pop().Item()
-	args := v.Estack().Pop().Item()
+	method := v.Estack().Pop().String()
+	args := v.Estack().Pop().Array()
 	flags := smartcontract.CallFlag(int32(v.Estack().Pop().BigInt().Int64()))
 	if flags&^smartcontract.All != 0 {
 		return errors.New("call flags out of range")
@@ -481,7 +474,7 @@ func contractCallEx(ic *interop.Context, v *vm.VM) error {
 	return contractCallExInternal(ic, v, h, method, args, flags)
 }
 
-func contractCallExInternal(ic *interop.Context, v *vm.VM, h []byte, method stackitem.Item, args stackitem.Item, f smartcontract.CallFlag) error {
+func contractCallExInternal(ic *interop.Context, v *vm.VM, h []byte, name string, args []stackitem.Item, f smartcontract.CallFlag) error {
 	u, err := util.Uint160DecodeBytesBE(h)
 	if err != nil {
 		return errors.New("invalid contract hash")
@@ -490,11 +483,6 @@ func contractCallExInternal(ic *interop.Context, v *vm.VM, h []byte, method stac
 	if err != nil {
 		return errors.New("contract not found")
 	}
-	bs, err := method.TryBytes()
-	if err != nil {
-		return err
-	}
-	name := string(bs)
 	if strings.HasPrefix(name, "_") {
 		return errors.New("invalid method name (starts with '_')")
 	}
@@ -504,17 +492,13 @@ func contractCallExInternal(ic *interop.Context, v *vm.VM, h []byte, method stac
 	}
 	curr, err := ic.DAO.GetContractState(v.GetCurrentScriptHash())
 	if err == nil {
-		if !curr.Manifest.CanCall(&cs.Manifest, string(bs)) {
+		if !curr.Manifest.CanCall(&cs.Manifest, name) {
 			return errors.New("disallowed method call")
 		}
 	}
 
-	arr, ok := args.Value().([]stackitem.Item)
-	if !ok {
-		return errors.New("second argument must be an array")
-	}
-	if len(arr) != len(md.Parameters) {
-		return fmt.Errorf("invalid argument count: %d (expected %d)", len(arr), len(md.Parameters))
+	if len(args) != len(md.Parameters) {
+		return fmt.Errorf("invalid argument count: %d (expected %d)", len(args), len(md.Parameters))
 	}
 
 	ic.Invocations[u]++
@@ -528,10 +512,10 @@ func contractCallExInternal(ic *interop.Context, v *vm.VM, h []byte, method stac
 	}
 	if isNative {
 		v.Estack().PushVal(args)
-		v.Estack().PushVal(method)
+		v.Estack().PushVal(name)
 	} else {
-		for i := len(arr) - 1; i >= 0; i-- {
-			v.Estack().PushVal(arr[i])
+		for i := len(args) - 1; i >= 0; i-- {
+			v.Estack().PushVal(args[i])
 		}
 		// use Jump not Call here because context was loaded in LoadScript above.
 		v.Jump(v.Context(), md.Offset)
diff --git a/pkg/core/interop_system_test.go b/pkg/core/interop_system_test.go
index aab9e5159..57d42c6e7 100644
--- a/pkg/core/interop_system_test.go
+++ b/pkg/core/interop_system_test.go
@@ -264,9 +264,9 @@ func TestRuntimeGetNotifications(t *testing.T) {
 		for i := range arr {
 			elem := arr[i].Value().([]stackitem.Item)
 			require.Equal(t, ic.Notifications[i].ScriptHash.BytesBE(), elem[0].Value())
-			name, err := elem[1].TryBytes()
+			name, err := stackitem.ToString(elem[1])
 			require.NoError(t, err)
-			require.Equal(t, ic.Notifications[i].Name, string(name))
+			require.Equal(t, ic.Notifications[i].Name, name)
 			require.Equal(t, ic.Notifications[i].Item, elem[2])
 		}
 	})
@@ -280,9 +280,9 @@ func TestRuntimeGetNotifications(t *testing.T) {
 		require.Equal(t, 1, len(arr))
 		elem := arr[0].Value().([]stackitem.Item)
 		require.Equal(t, h, elem[0].Value())
-		name, err := elem[1].TryBytes()
+		name, err := stackitem.ToString(elem[1])
 		require.NoError(t, err)
-		require.Equal(t, ic.Notifications[1].Name, string(name))
+		require.Equal(t, ic.Notifications[1].Name, name)
 		require.Equal(t, ic.Notifications[1].Item, elem[2])
 	})
 }
@@ -443,7 +443,14 @@ func TestContractCall(t *testing.T) {
 			for i := range args {
 				v.Estack().PushVal(args[i])
 			}
-			require.Error(t, contractCall(ic, v))
+			// interops can both return error and panic,
+			// we don't care which kind of error has occured
+			require.Panics(t, func() {
+				err := contractCall(ic, v)
+				if err != nil {
+					panic(err)
+				}
+			})
 		}
 	}
 
diff --git a/pkg/core/native/interop.go b/pkg/core/native/interop.go
index 63e3b1da4..5e1d23515 100644
--- a/pkg/core/native/interop.go
+++ b/pkg/core/native/interop.go
@@ -35,7 +35,7 @@ func Deploy(ic *interop.Context, _ *vm.VM) error {
 
 // Call calls specified native contract method.
 func Call(ic *interop.Context, v *vm.VM) error {
-	name := string(v.Estack().Pop().Bytes())
+	name := v.Estack().Pop().String()
 	var c interop.Contract
 	for _, ctr := range ic.Natives {
 		if ctr.Metadata().Name == name {
@@ -50,7 +50,7 @@ func Call(ic *interop.Context, v *vm.VM) error {
 	if !h.Equals(c.Metadata().Hash) {
 		return errors.New("it is not allowed to use Neo.Native.Call directly to call native contracts. System.Contract.Call should be used")
 	}
-	operation := string(v.Estack().Pop().Bytes())
+	operation := v.Estack().Pop().String()
 	args := v.Estack().Pop().Array()
 	m, ok := c.Metadata().Methods[operation]
 	if !ok {
diff --git a/pkg/vm/interop.go b/pkg/vm/interop.go
index bf04a2e8e..1d68c46aa 100644
--- a/pkg/vm/interop.go
+++ b/pkg/vm/interop.go
@@ -67,16 +67,16 @@ func defaultSyscallHandler(v *VM, id uint32) error {
 
 // runtimeLog handles the syscall "System.Runtime.Log" for printing and logging stuff.
 func runtimeLog(vm *VM) error {
-	item := vm.Estack().Pop()
-	fmt.Printf("NEO-GO-VM (log) > %s\n", item.Value())
+	msg := vm.Estack().Pop().String()
+	fmt.Printf("NEO-GO-VM (log) > %s\n", msg)
 	return nil
 }
 
 // runtimeNotify handles the syscall "System.Runtime.Notify" for printing and logging stuff.
 func runtimeNotify(vm *VM) error {
-	name := vm.Estack().Pop().Bytes()
+	name := vm.Estack().Pop().String()
 	item := vm.Estack().Pop()
-	fmt.Printf("NEO-GO-VM (notify) > [%s] %s\n", string(name), item.Value())
+	fmt.Printf("NEO-GO-VM (notify) > [%s] %s\n", name, item.Value())
 	return nil
 }
 
diff --git a/pkg/vm/stack.go b/pkg/vm/stack.go
index 44e9d6d94..a66058d3f 100644
--- a/pkg/vm/stack.go
+++ b/pkg/vm/stack.go
@@ -96,6 +96,16 @@ func (e *Element) Bytes() []byte {
 	return bs
 }
 
+// String attempts to get string from the element value.
+// It is assumed to be use in interops and panics if string is not a valid UTF-8 byte sequence.
+func (e *Element) String() string {
+	s, err := stackitem.ToString(e.value)
+	if err != nil {
+		panic(err)
+	}
+	return s
+}
+
 // Array attempts to get the underlying value of the element as an array of
 // other items. Will panic if the item type is different which will be caught
 // by the VM.
diff --git a/pkg/vm/stackitem/item.go b/pkg/vm/stackitem/item.go
index 0d6c86851..4cd138e93 100644
--- a/pkg/vm/stackitem/item.go
+++ b/pkg/vm/stackitem/item.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"math/big"
 	"reflect"
+	"unicode/utf8"
 
 	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/bigint"
@@ -120,6 +121,18 @@ func Make(v interface{}) Item {
 	}
 }
 
+// ToString converts Item to string if it is a valid UTF-8.
+func ToString(item Item) (string, error) {
+	bs, err := item.TryBytes()
+	if err != nil {
+		return "", err
+	}
+	if !utf8.Valid(bs) {
+		return "", errors.New("not a valid UTF-8")
+	}
+	return string(bs), nil
+}
+
 // convertPrimitive converts primitive item to a specified type.
 func convertPrimitive(item Item, typ Type) (Item, error) {
 	if item.Type() == typ {
diff --git a/pkg/vm/stackitem/json.go b/pkg/vm/stackitem/json.go
index 81b67f769..97d25f883 100644
--- a/pkg/vm/stackitem/json.go
+++ b/pkg/vm/stackitem/json.go
@@ -64,9 +64,17 @@ func toJSON(buf *io.BufBinWriter, item Item) {
 	case *Map:
 		w.WriteB('{')
 		for i := range it.value {
-			bs, _ := it.value[i].Key.TryBytes() // map key can always be converted to []byte
+			// map key can always be converted to []byte
+			// but are not always a valid UTF-8.
+			key, err := ToString(it.value[i].Key)
+			if err != nil {
+				if buf.Err == nil {
+					buf.Err = err
+				}
+				return
+			}
 			w.WriteB('"')
-			w.WriteBytes(bs)
+			w.WriteBytes([]byte(key))
 			w.WriteBytes([]byte(`":`))
 			toJSON(buf, it.value[i].Value)
 			if i < len(it.value)-1 {