diff --git a/runtime/marshal_json_test.go b/runtime/marshal_json_test.go
index 490e66bab83..5037aea9348 100644
--- a/runtime/marshal_json_test.go
+++ b/runtime/marshal_json_test.go
@@ -197,6 +197,8 @@ var (
 		{data: "", json: `""`},
 		{data: proto.String(""), json: `""`},
 		{data: "foo", json: `"foo"`},
+		{data: []byte("foo"), json: `"Zm9v"`},
+		{data: []byte{}, json: `""`},
 		{data: proto.String("foo"), json: `"foo"`},
 		{data: int32(-1), json: "-1"},
 		{data: proto.Int32(-1), json: "-1"},
diff --git a/runtime/marshal_jsonpb.go b/runtime/marshal_jsonpb.go
index 7387c8e3976..524ea057ccb 100644
--- a/runtime/marshal_jsonpb.go
+++ b/runtime/marshal_jsonpb.go
@@ -280,6 +280,17 @@ func decodeNonProtoField(d *json.Decoder, unmarshaler protojson.UnmarshalOptions
 		return nil
 	}
 	if rv.Kind() == reflect.Slice {
+		if rv.Type().Elem().Kind() == reflect.Uint8 {
+			var sl []byte
+			if err := d.Decode(&sl); err != nil {
+				return err
+			}
+			if sl != nil {
+				rv.SetBytes(sl)
+			}
+			return nil
+		}
+
 		var sl []json.RawMessage
 		if err := d.Decode(&sl); err != nil {
 			return err
diff --git a/runtime/marshal_jsonpb_test.go b/runtime/marshal_jsonpb_test.go
index 2d5f8bedd4c..d82290c1416 100644
--- a/runtime/marshal_jsonpb_test.go
+++ b/runtime/marshal_jsonpb_test.go
@@ -523,6 +523,8 @@ var (
 		{data: uint64(1), json: "1"},
 		{data: proto.Uint64(1), json: "1"},
 		{data: "abc", json: `"abc"`},
+		{data: []byte("abc"), json: `"YWJj"`},
+		{data: []byte{}, json: `""`},
 		{data: proto.String("abc"), json: `"abc"`},
 		{data: float32(1.5), json: "1.5"},
 		{data: proto.Float32(1.5), json: "1.5"},