diff --git a/ChangeLog b/ChangeLog
index ad39501d2c..3ea3490517 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Dec  3 22:40:59 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* iseq.c (simple_default_value): returns simplest assignment only.
+	  [ruby-core:20237]
+
 Wed Dec  3 21:30:06 2008  Tanaka Akira  <akr@fsij.org>
 
 	* process.c (check_exec_redirect): accept :in, :out, :err as redirect
diff --git a/iseq.c b/iseq.c
index 54ae01f8c2..351ea41fd9 100644
--- a/iseq.c
+++ b/iseq.c
@@ -1292,13 +1292,12 @@ simple_default_value(const VALUE *seq, const VALUE *eseq)
       got:
 	switch (*seq++) {
 	  case BIN(setlocal):
-	    if ((seq+=1) != eseq) return Qundef;
+	    if ((seq+=1) == eseq) return val;
 	    break;
 	  case BIN(setdynamic):
-	    if ((seq+=2) != eseq) return Qundef;
+	    if ((seq+=2) == eseq) return val;
 	    break;
 	}
-	return val;
       default:
 	return Qundef;
     }