diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index f2b27734d..eb80d4ee9 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -1159,11 +1159,17 @@ func (bc *Blockchain) ApplyPolicyToTxSet(txes []*transaction.Transaction) []*tra
 	if maxTx != 0 && len(txes) > int(maxTx) {
 		txes = txes[:maxTx]
 	}
+	maxBlockSize := bc.contracts.Policy.GetMaxBlockSizeInternal(bc.dao)
 	maxBlockSysFee := bc.contracts.Policy.GetMaxBlockSystemFeeInternal(bc.dao)
-	var sysFee int64
+	var (
+		blockSize uint32
+		sysFee    int64
+	)
+	blockSize = uint32(io.GetVarSize(new(block.Block)) + io.GetVarSize(len(txes)+1))
 	for i, tx := range txes {
+		blockSize += uint32(io.GetVarSize(tx))
 		sysFee += tx.SystemFee
-		if sysFee > maxBlockSysFee {
+		if blockSize > maxBlockSize || sysFee > maxBlockSysFee {
 			txes = txes[:i]
 			break
 		}
diff --git a/pkg/core/native/policy.go b/pkg/core/native/policy.go
index c7258da0c..9d7c31cad 100644
--- a/pkg/core/native/policy.go
+++ b/pkg/core/native/policy.go
@@ -225,12 +225,17 @@ func (p *Policy) GetMaxTransactionsPerBlockInternal(dao dao.DAO) uint32 {
 
 // getMaxBlockSize is Policy contract method and returns maximum block size.
 func (p *Policy) getMaxBlockSize(ic *interop.Context, _ []stackitem.Item) stackitem.Item {
+	return stackitem.NewBigInteger(big.NewInt(int64(p.GetMaxBlockSizeInternal(ic.DAO))))
+}
+
+// GetMaxBlockSizeInternal returns maximum block size.
+func (p *Policy) GetMaxBlockSizeInternal(dao dao.DAO) uint32 {
 	p.lock.RLock()
 	defer p.lock.RUnlock()
 	if p.isValid {
-		return stackitem.NewBigInteger(big.NewInt(int64(p.maxBlockSize)))
+		return p.maxBlockSize
 	}
-	return stackitem.NewBigInteger(big.NewInt(int64(p.getUint32WithKey(ic.DAO, maxBlockSizeKey))))
+	return p.getUint32WithKey(dao, maxBlockSizeKey)
 }
 
 // getFeePerByte is Policy contract method and returns required transaction's fee
diff --git a/pkg/core/native_policy_test.go b/pkg/core/native_policy_test.go
index 58388dbb7..edf0b7b9e 100644
--- a/pkg/core/native_policy_test.go
+++ b/pkg/core/native_policy_test.go
@@ -53,7 +53,12 @@ func TestMaxBlockSize(t *testing.T) {
 	chain := newTestChain(t)
 	defer chain.Close()
 
-	t.Run("get", func(t *testing.T) {
+	t.Run("get, internal method", func(t *testing.T) {
+		n := chain.contracts.Policy.GetMaxBlockSizeInternal(chain.dao)
+		require.Equal(t, 1024*256, int(n))
+	})
+
+	t.Run("get, contract method", func(t *testing.T) {
 		res, err := invokeNativePolicyMethod(chain, "getMaxBlockSize")
 		require.NoError(t, err)
 		checkResult(t, res, smartcontract.Parameter{