diff --git a/ChangeLog b/ChangeLog
index 089d34097f..aed15cf971 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jun 30 14:41:36 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* gc.c (rb_newobj): prohibit call of rb_newobj() during gc when
+	  USE_VALUE_CACHE is not defined (normal case).
+
 Mon Jun 30 10:28:33 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* ext/syslog/syslog.c (syslog_write): syslog operations should be
diff --git a/gc.c b/gc.c
index 966aaa1933..31c1547e34 100644
--- a/gc.c
+++ b/gc.c
@@ -732,6 +732,8 @@ rb_newobj(void)
     return v;
 #else
     rb_objspace_t *objspace = &rb_objspace;
+    if (during_gc)
+        rb_bug("object allocation during garbage collection phase");
     return rb_newobj_from_heap(objspace);
 #endif
 }