diff --git a/iseq.c b/iseq.c
index d267c7e08b..3d18fb597a 100644
--- a/iseq.c
+++ b/iseq.c
@@ -354,11 +354,13 @@ rb_iseq_mark_and_move(rb_iseq_t *iseq, bool reference_updating)
             }
         }
 
-        if (body->param.flags.has_kw && ISEQ_COMPILE_DATA(iseq) == NULL) {
+        if (body->param.flags.has_kw && body->param.keyword != NULL) {
             const struct rb_iseq_param_keyword *const keyword = body->param.keyword;
 
-            for (int j = 0, i = keyword->required_num; i < keyword->num; i++, j++) {
-                rb_gc_mark_and_move(&keyword->default_values[j]);
+            if (keyword->default_values != NULL) {
+                for (int j = 0, i = keyword->required_num; i < keyword->num; i++, j++) {
+                    rb_gc_mark_and_move(&keyword->default_values[j]);
+                }
             }
         }