diff --git a/ChangeLog b/ChangeLog
index 6e1f99980d..66c26215e4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Nov 27 17:54:57 2013  Koichi Sasada  <ko1@atdot.net>
+
+	* gc.c (gc_mark_stacked_objects): check only when check_mode > 0.
+
 Wed Nov 27 16:07:19 2013  Aman Gupta <ruby@tmm1.net>
 
 	* test/ruby/test_gc.rb (class TestGc): Fix warning in
diff --git a/gc.c b/gc.c
index 0adf549334..79cd7971f8 100644
--- a/gc.c
+++ b/gc.c
@@ -3908,7 +3908,7 @@ gc_mark_stacked_objects(rb_objspace_t *objspace)
 
     if (!mstack->index) return;
     while (pop_mark_stack(mstack, &obj)) {
-	if (!gc_marked(objspace, obj)) {
+	if (RGENGC_CHECK_MODE > 0 && !gc_marked(objspace, obj)) {
 	    rb_bug("gc_mark_stacked_objects: %p (%s) is infant, but not marked.", (void *)obj, obj_type_name(obj));
 	}
         gc_mark_children(objspace, obj);