diff --git a/ChangeLog b/ChangeLog
index 6a22165df5..fb55fb76c0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Jan 28 13:04:38 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* configure.in (--with-valgrind): Fixed r29683. Now this option
+	  is really default on.
+
 Fri Jan 28 12:05:48 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* configure.in: Add #include<sys/stat.h> when struct stat is
diff --git a/configure.in b/configure.in
index fbd9283561..34af64062f 100644
--- a/configure.in
+++ b/configure.in
@@ -1836,9 +1836,9 @@ AS_CASE(["$target_os"],
 AC_CHECK_FUNCS(backtrace)
 
 AC_ARG_WITH(valgrind,
-        AS_HELP_STRING([--with-valgrind],[enable valgrind memcheck support]),
-        ruby_cv_with_valgrind=yes,ruby_cv_with_valgrind=no)
-AS_IF([test x$ruby_cv_with_valgrind != xno],
+        AS_HELP_STRING([--without-valgrind],[disable valgrind memcheck support]),
+        [], with_valgrind=yes)
+AS_IF([test x$with_valgrind != xno],
         [AC_CHECK_HEADERS(valgrind/memcheck.h)])
 
 dnl }