diff --git a/ChangeLog b/ChangeLog
index 34d11eb65d..6a7c2f9ab2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Sep  7 06:31:51 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* file.c (file_expand_path): applied a patch from Nobuhiro Tachino
+	  in [ruby-dev:35948].  fix #491
+
 Sun Sep  7 03:37:05 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* parse.y (f_block_optarg): allow default for block parameters as
diff --git a/file.c b/file.c
index 33327a6f96..dbaafd2e87 100644
--- a/file.c
+++ b/file.c
@@ -2728,8 +2728,7 @@ file_expand_path(VALUE fname, VALUE dname, int abs_mode, VALUE result)
     if (p > buf && p[-1] == '/')
 	--p;
     else {
-	++buflen;
-	BUFCHECK(bdiff >= buflen);
+	BUFCHECK(bdiff + 1 >= buflen);
 	*p = '/';
     }