diff --git a/ChangeLog b/ChangeLog
index 67c0d1fbae..c08b060138 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Jul  6 00:29:27 2010  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* string.c (NONASCII_MASK): NONASCII_MASK must be unsigned.
+	  [ruby-dev:41782]
+
 Mon Jul  5 16:05:39 2010  Akinori MUSHA  <knu@iDaemons.org>
 
 	* vm_method.c (rb_method_boundp): Return false for protected
diff --git a/string.c b/string.c
index ba4ce86087..8cfbb56bdf 100644
--- a/string.c
+++ b/string.c
@@ -141,7 +141,7 @@ static inline const char *
 search_nonascii(const char *p, const char *e)
 {
 #if SIZEOF_VALUE == 8
-# define NONASCII_MASK 0x8080808080808080LL
+# define NONASCII_MASK 0x8080808080808080ULL
 #elif SIZEOF_VALUE == 4
 # define NONASCII_MASK 0x80808080UL
 #endif