diff --git a/ChangeLog b/ChangeLog
index 869796b35f..a7f4de32a0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Mar  4 16:29:06 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* parse.y (parser_yylex): disallow non digits '0o' expression.
+
 Tue Mar 04 14:35:12 2008  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* io.c (open_key_args): use rb_io_open_with_args instead of rb_f_open.
diff --git a/parse.y b/parse.y
index 88e72de4bf..e1c047029b 100644
--- a/parse.y
+++ b/parse.y
@@ -6634,7 +6634,7 @@ parser_yylex(struct parser_params *parser)
 		if (c == 'o' || c == 'O') {
 		    /* prefixed octal */
 		    c = nextc();
-		    if (c == '_') {
+		    if (c == '_' || !ISDIGIT(c)) {
 			yyerror("numeric literal without digits");
 		    }
 		}