diff --git a/pkg/smartcontract/param_type.go b/pkg/smartcontract/param_type.go
index 403a48649..cb32c72ab 100644
--- a/pkg/smartcontract/param_type.go
+++ b/pkg/smartcontract/param_type.go
@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"math/big"
 	"strings"
+	"unicode/utf8"
 
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
@@ -203,8 +204,10 @@ func (pt ParamType) Match(v stackitem.Item) bool {
 		return vt == stackitem.BooleanT
 	case IntegerType:
 		return vt == stackitem.IntegerT
-	case ByteArrayType, StringType:
+	case ByteArrayType:
 		return vt == stackitem.ByteArrayT || vt == stackitem.BufferT || vt == stackitem.AnyT
+	case StringType:
+		return (vt == stackitem.ByteArrayT || vt == stackitem.BufferT) && utf8.Valid(v.Value().([]byte))
 	case Hash160Type:
 		return checkBytesWithLen(vt, v, Hash160Len)
 	case Hash256Type:
diff --git a/pkg/smartcontract/param_type_test.go b/pkg/smartcontract/param_type_test.go
index 9d3e51d2f..4f754d5ae 100644
--- a/pkg/smartcontract/param_type_test.go
+++ b/pkg/smartcontract/param_type_test.go
@@ -428,25 +428,27 @@ func TestConvertToStackitemType(t *testing.T) {
 
 func TestParamTypeMatch(t *testing.T) {
 	for itm, pt := range map[stackitem.Item]ParamType{
-		&stackitem.Pointer{}:      BoolType,
-		&stackitem.Pointer{}:      MapType,
-		stackitem.Make(0):         BoolType,
-		stackitem.Make(0):         ByteArrayType,
-		stackitem.Make(0):         StringType,
-		stackitem.Make(false):     ByteArrayType,
-		stackitem.Make(true):      StringType,
-		stackitem.Make([]byte{1}): Hash160Type,
-		stackitem.Make([]byte{1}): Hash256Type,
-		stackitem.Make([]byte{1}): PublicKeyType,
-		stackitem.Make([]byte{1}): SignatureType,
-		stackitem.Make(0):         Hash160Type,
-		stackitem.Make(0):         Hash256Type,
-		stackitem.Make(0):         PublicKeyType,
-		stackitem.Make(0):         SignatureType,
-		stackitem.Make(0):         ArrayType,
-		stackitem.Make(0):         MapType,
-		stackitem.Make(0):         InteropInterfaceType,
-		stackitem.Make(0):         VoidType,
+		&stackitem.Pointer{}:         BoolType,
+		&stackitem.Pointer{}:         MapType,
+		stackitem.Make(0):            BoolType,
+		stackitem.Make(0):            ByteArrayType,
+		stackitem.Make(0):            StringType,
+		stackitem.Make(false):        ByteArrayType,
+		stackitem.Make(true):         StringType,
+		stackitem.Make([]byte{1}):    Hash160Type,
+		stackitem.Make([]byte{1}):    Hash256Type,
+		stackitem.Make([]byte{1}):    PublicKeyType,
+		stackitem.Make([]byte{1}):    SignatureType,
+		stackitem.Make(0):            Hash160Type,
+		stackitem.Make(0):            Hash256Type,
+		stackitem.Make(0):            PublicKeyType,
+		stackitem.Make(0):            SignatureType,
+		stackitem.Make(0):            ArrayType,
+		stackitem.Make(0):            MapType,
+		stackitem.Make(0):            InteropInterfaceType,
+		stackitem.Make(0):            VoidType,
+		stackitem.Null{}:             StringType,
+		stackitem.Make([]byte{0x80}): StringType, // non utf-8
 	} {
 		require.Falsef(t, pt.Match(itm), "%s - %s", pt.String(), itm.String())
 	}
@@ -456,11 +458,11 @@ func TestParamTypeMatch(t *testing.T) {
 		stackitem.Make(0):                          IntegerType,
 		stackitem.Make(100500):                     IntegerType,
 		stackitem.Make([]byte{1}):                  ByteArrayType,
+		stackitem.Make([]byte{0x80}):               ByteArrayType, // non utf-8
 		stackitem.Make([]byte{1}):                  StringType,
 		stackitem.NewBuffer([]byte{1}):             ByteArrayType,
 		stackitem.NewBuffer([]byte{1}):             StringType,
 		stackitem.Null{}:                           ByteArrayType,
-		stackitem.Null{}:                           StringType,
 		stackitem.Make(util.Uint160{}.BytesBE()):   Hash160Type,
 		stackitem.Make(util.Uint256{}.BytesBE()):   Hash256Type,
 		stackitem.Null{}:                           Hash160Type,