diff --git a/ChangeLog b/ChangeLog
index 054e47da34..ed8a0df3e3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Aug 12 23:07:21 2013  Masaya Tarui  <tarui@ruby-lang.org>
+
+	* gc.c (gc_marks_test): inhibit gc for st's operation.
+
 Mon Aug 12 15:59:50 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* parse.y (parser_whole_match_p): treat CR in middle of a line as a
diff --git a/gc.c b/gc.c
index 4ba997b207..6cb2594a2c 100644
--- a/gc.c
+++ b/gc.c
@@ -3550,6 +3550,8 @@ gc_marks_test(rb_objspace_t *objspace)
      *   exported_bitmap: after minor marking
      */
 
+    /* inhibit gc for st's operation */
+    dont_gc = 1;
 
     if(!monitored_object_table)
 	monitored_object_table = st_init_numtable();
@@ -3608,6 +3610,7 @@ gc_marks_test(rb_objspace_t *objspace)
 	gc_free_exported_bitmaps(objspace, exported_bitmaps);
 	objspace->rgengc.have_saved_bitmaps = FALSE;
     }
+    dont_gc = 0;
 }
 #endif /* RGENGC_CHECK_MODE >= 2 */