diff --git a/ChangeLog b/ChangeLog
index 771e09db8d..71a9f993bd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Sep  1 22:07:04 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* ruby.h (RSTRING_EMBED_LEN_MASK): uses 5 bits to support 64bit
+	  environment.  [ruby-dev:29369]
+
 Fri Sep  1 22:02:08 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* string.c (rb_str_resize): should copy embedded string to
diff --git a/ruby.h b/ruby.h
index e0025083e5..6a2d2db4c0 100644
--- a/ruby.h
+++ b/ruby.h
@@ -378,7 +378,7 @@ struct RString {
     } as;
 };
 #define RSTRING_NOEMBED FL_USER1
-#define RSTRING_EMBED_LEN_MASK (FL_USER2|FL_USER3|FL_USER4|FL_USER5)
+#define RSTRING_EMBED_LEN_MASK (FL_USER2|FL_USER3|FL_USER4|FL_USER5|FL_USER6)
 #define RSTRING_EMBED_LEN_SHIFT (FL_USHIFT+2)
 #define RSTRING_LEN(str) \
     (!(RBASIC(str)->flags & RSTRING_NOEMBED) ? \