diff --git a/imemo.c b/imemo.c
index f573967817..a0ed567719 100644
--- a/imemo.c
+++ b/imemo.c
@@ -309,7 +309,7 @@ rb_imemo_mark_and_move(VALUE obj, bool reference_updating)
             }
         }
         else {
-            if (vm_cc_super_p(cc) || vm_cc_refinement_p(cc)) {
+            if (cc->klass && (vm_cc_super_p(cc) || vm_cc_refinement_p(cc))) {
                 rb_gc_mark_movable((VALUE)cc->cme_);
                 rb_gc_mark_movable((VALUE)cc->klass);
             }