diff --git a/ChangeLog b/ChangeLog
index d77518cb41..df65c66188 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,8 @@
-Sun Jun 20 15:14:05 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Sun Jun 20 16:17:24 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* id.c (Init_id): add underscore name.
+
+	* parse.y (warn_unused_var): ignore underscore name.
 
 	* parse.y (warn_unused_var): use same format as shadowing local
 	  variable.
diff --git a/id.c b/id.c
index 2111751a37..89ae4a4e77 100644
--- a/id.c
+++ b/id.c
@@ -47,4 +47,5 @@ Init_id(void)
     REGISTER_SYMID(idSend, "send");
     REGISTER_SYMID(id__send__, "__send__");
     REGISTER_SYMID(idInitialize, "initialize");
+    REGISTER_SYMID(idUScore, "_");
 }
diff --git a/parse.y b/parse.y
index 77cc71cf65..9969092e18 100644
--- a/parse.y
+++ b/parse.y
@@ -8229,10 +8229,7 @@ assignable_gen(struct parser_params *parser, ID id, NODE *val)
 static ID
 shadowing_lvar_gen(struct parser_params *parser, ID name)
 {
-    ID uscore;
-
-    CONST_ID(uscore, "_");
-    if (uscore == name) return name;
+    if (idUScore == name) return name;
     if (dyna_in_block()) {
 	if (dvar_curr(name)) {
 	    yyerror("duplicated argument name");
@@ -8935,6 +8932,7 @@ warn_unused_var(struct parser_params *parser, struct local_vars *local)
     }
     for (i = 0; i < cnt; ++i) {
 	if (!v[i] || (u[i] & LVAR_USED)) continue;
+	if (idUScore == v[i]) continue;
 	rb_compile_warn(ruby_sourcefile, (int)u[i], "assigned but unused variable - %s", rb_id2name(v[i]));
     }
 }
diff --git a/template/id.h.tmpl b/template/id.h.tmpl
index 11df0507f4..b91292a103 100644
--- a/template/id.h.tmpl
+++ b/template/id.h.tmpl
@@ -100,6 +100,7 @@ enum ruby_method_ids {
     tSend,
     t__send__,
     tInitialize,
+    tUScore,
 #if SUPPORT_JOKE
     tBitblt,
     tAnswer,
@@ -120,7 +121,9 @@ enum ruby_method_ids {
     TOKEN2ID(Lambda),
     TOKEN2ID(Send),
     TOKEN2ID(__send__),
-    TOKEN2ID(Initialize)
+    TOKEN2ID(Initialize),
+    TOKEN2ID(UScore),
+    TOKEN2ID(LAST_ID)
 };
 
 #ifdef tLAST_TOKEN