diff --git a/ChangeLog b/ChangeLog
index 5ebbedf95b..3273cfbdab 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Feb 19 22:37:42 2011  CHIKANAGA Tomoyuki  <nagachika00@gmail.com>
+
+	* vm_insnhelper.c (vm_check_if_namespace): guard temporary object
+	  from GC.
+
 Sat Feb 19 06:36:27 2011  Aaron Patterson <aaron@tenderlovemaking.com>
 
 	* lib/test/unit.rb: partial revert of r30849. [ruby-core:32864]
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 8cd066f532..139a2a24ab 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1135,13 +1135,15 @@ vm_get_const_base(const rb_iseq_t *iseq, const VALUE *lfp, const VALUE *dfp)
 static inline void
 vm_check_if_namespace(VALUE klass)
 {
+    VALUE str;
     switch (TYPE(klass)) {
       case T_CLASS:
       case T_MODULE:
 	break;
       default:
+	str = rb_inspect(klass);
 	rb_raise(rb_eTypeError, "%s is not a class/module",
-		 RSTRING_PTR(rb_inspect(klass)));
+		 RSTRING_PTR(RB_GC_GUARD(str)));
     }
 }