diff --git a/src/typval.c b/src/typval.c
index 59ac611..b9f8f1c 100644
--- a/src/typval.c
+++ b/src/typval.c
@@ -2095,6 +2095,9 @@
 	|| (tv->v_type == VAR_LIST
 		&& tv->vval.v_list != NULL
 		&& (tv->vval.v_list->lv_lock & VAR_LOCKED))
+	|| (tv->v_type == VAR_TUPLE
+		&& tv->vval.v_tuple != NULL
+		&& (tv->vval.v_tuple->tv_lock & VAR_LOCKED))
 	|| (tv->v_type == VAR_DICT
 		&& tv->vval.v_dict != NULL
 		&& (tv->vval.v_dict->dv_lock & VAR_LOCKED));