diff --git a/ChangeLog b/ChangeLog
index 7b4ce9af8e..cfd295c69c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,6 @@
-Fri Oct 30 04:44:01 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Fri Oct 30 04:47:26 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* include/ruby/ruby.h (RSTRING_END): trivial optimization.
 
 	* string.c (rb_str_sub_bang): trivial optimization.
 
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 19f146e4ad..55836a8fd4 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -619,7 +619,12 @@ struct RString {
     (!(RBASIC(str)->flags & RSTRING_NOEMBED) ? \
      RSTRING(str)->as.ary : \
      RSTRING(str)->as.heap.ptr)
-#define RSTRING_END(str) (RSTRING_PTR(str)+RSTRING_LEN(str))
+#define RSTRING_END(str) \
+    (!(RBASIC(str)->flags & RSTRING_NOEMBED) ? \
+     (RSTRING(str)->as.ary + \
+      ((RBASIC(str)->flags >> RSTRING_EMBED_LEN_SHIFT) & \
+       (RSTRING_EMBED_LEN_MASK >> RSTRING_EMBED_LEN_SHIFT))) : \
+     (RSTRING(str)->as.heap.ptr + RSTRING(str)->as.heap.len))
 
 #define RARRAY_EMBED_LEN_MAX 3
 struct RArray {