diff --git a/pkg/core/mpt/extension.go b/pkg/core/mpt/extension.go
index 026201655..7cb0bb7f0 100644
--- a/pkg/core/mpt/extension.go
+++ b/pkg/core/mpt/extension.go
@@ -11,8 +11,14 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/util"
 )
 
-// MaxKeyLength is the max length of the extension node key.
-const MaxKeyLength = (storage.MaxStorageKeyLen + 4) * 2
+const (
+	// maxPathLength is the max length of the extension node key.
+	maxPathLength = (storage.MaxStorageKeyLen + 4) * 2
+
+	// MaxKeyLength is the max length of the key to put in trie
+	// before transforming to nibbles.
+	MaxKeyLength = maxPathLength / 2
+)
 
 // ExtensionNode represents MPT's extension node.
 type ExtensionNode struct {
@@ -48,7 +54,7 @@ func (e *ExtensionNode) Bytes() []byte {
 // DecodeBinary implements io.Serializable.
 func (e *ExtensionNode) DecodeBinary(r *io.BinReader) {
 	sz := r.ReadVarUint()
-	if sz > MaxKeyLength {
+	if sz > maxPathLength {
 		r.Err = fmt.Errorf("extension node key is too big: %d", sz)
 		return
 	}
diff --git a/pkg/core/mpt/node.go b/pkg/core/mpt/node.go
index 2d2c42807..5f8aed265 100644
--- a/pkg/core/mpt/node.go
+++ b/pkg/core/mpt/node.go
@@ -96,7 +96,7 @@ func (n *NodeObject) UnmarshalJSON(data []byte) error {
 		key, err := unmarshalHex(keyRaw)
 		if err != nil {
 			return err
-		} else if len(key) > MaxKeyLength {
+		} else if len(key) > maxPathLength {
 			return errors.New("extension key is too big")
 		}
 
diff --git a/pkg/core/mpt/node_test.go b/pkg/core/mpt/node_test.go
index 74c0247a2..0af0509a9 100644
--- a/pkg/core/mpt/node_test.go
+++ b/pkg/core/mpt/node_test.go
@@ -61,7 +61,7 @@ func TestNode_Serializable(t *testing.T) {
 			t.Run("WithType", getTestFuncEncode(true, &NodeObject{e}, new(NodeObject)))
 		})
 		t.Run("BigKey", getTestFuncEncode(false,
-			NewExtensionNode(random.Bytes(MaxKeyLength+1), NewLeafNode(random.Bytes(10))), new(ExtensionNode)))
+			NewExtensionNode(random.Bytes(maxPathLength+1), NewLeafNode(random.Bytes(10))), new(ExtensionNode)))
 	})
 
 	t.Run("Branch", func(t *testing.T) {
diff --git a/pkg/core/mpt/trie_test.go b/pkg/core/mpt/trie_test.go
index bbb3b9828..405c501dc 100644
--- a/pkg/core/mpt/trie_test.go
+++ b/pkg/core/mpt/trie_test.go
@@ -161,7 +161,7 @@ func TestTrie_PutInvalid(t *testing.T) {
 	key, value := []byte("key"), []byte("value")
 
 	// big key
-	require.Error(t, tr.Put(make([]byte, MaxKeyLength+1), value))
+	require.Error(t, tr.Put(make([]byte, maxPathLength+1), value))
 
 	// big value
 	require.Error(t, tr.Put(key, make([]byte, MaxValueLength+1)))