diff --git a/ChangeLog b/ChangeLog
index 12b6527e22..f9487cf0f4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,8 @@ Tue Jan  9 03:54:38 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 	* string.c (rb_str_upto): String#upto from empty string makes
 	  inifinite loop.  [ruby-core:09864]
 
+	* string.c (rb_str_upto): use RSTRING_LEN().
+
 Sun Jan  7 18:36:05 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* thread.c (rb_thread_stop_timer_thread(), rb_thread_reset_timer_thread(),
diff --git a/string.c b/string.c
index 49eddf6148..8046145178 100644
--- a/string.c
+++ b/string.c
@@ -1568,7 +1568,7 @@ rb_str_upto(VALUE beg, VALUE end, int excl)
 	StringValue(current);
 	if (excl && rb_str_equal(current, end)) break;
 	StringValue(current);
-	if (RSTRING_LEN(current) > RSTRING_LEN(end) || RSTRING(current)->len == 0)
+	if (RSTRING_LEN(current) > RSTRING_LEN(end) || RSTRING_LEN(current) == 0)
 	    break;
     }