diff --git a/ChangeLog b/ChangeLog
index 14adb17f51..0abb21183d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Sep 20 18:08:51 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* vm_insnhelper.c (vm_get_cvar_base): reduce duplicated checks and
+	  move a warning outside the loop.
+
 Mon Sep 19 18:55:51 2011  Ayumu AIZAWA  <ayumu.aizawa@gmail.com>
 
 	* lib/fileutils.rb (module FileUtils): improve performance of
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 98f6ea93e1..9a6661e79b 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1235,14 +1235,17 @@ vm_get_cvar_base(NODE *cref)
 {
     VALUE klass;
 
-    while (cref && cref->nd_next &&
+    if (!cref) {
+	rb_bug("vm_get_cvar_base: no cref");
+    }
+
+    while (cref->nd_next &&
 	   (NIL_P(cref->nd_clss) || FL_TEST(cref->nd_clss, FL_SINGLETON) ||
 	    (cref->flags & NODE_FL_CREF_PUSHED_BY_EVAL))) {
 	cref = cref->nd_next;
-
-	if (!cref->nd_next) {
-	    rb_warn("class variable access from toplevel");
-	}
+    }
+    if (!cref->nd_next) {
+	rb_warn("class variable access from toplevel");
     }
 
     klass = cref->nd_clss;