diff --git a/ChangeLog b/ChangeLog
index acee9ae225..aecc325e2f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sun Mar  1 18:10:34 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* configure.in (rb_cv_broken_memmem): check before adding the
+	  result HAVE_MEMMEM macro to confdefs.h, so that configured
+	  results will be stable.
+
 Sun Mar  1 11:17:56 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* gc.c (id2ref): prohibit from accessing internal objects.
diff --git a/configure.in b/configure.in
index 7e8b91599c..2824993da7 100644
--- a/configure.in
+++ b/configure.in
@@ -2027,6 +2027,33 @@ else
   AC_LIBOBJ([signbit])
 fi
 
+AC_CACHE_CHECK(for broken memmem, rb_cv_broken_memmem, [
+    AC_TRY_RUN([
+@%:@include <string.h>
+
+int
+main(int argc, char **argv)
+{
+    const char *str = "hogefugafoobar";
+    const char *rs = "foo";
+    const char *empty = "";
+    char *p;
+
+    p = memmem(str, strlen(str), rs, strlen(rs));
+    if (p == str+8) {
+	p = memmem(str, strlen(str), empty, strlen(empty));
+	if (p == str)
+	    return 0;
+    }
+    return 1;
+}
+    ],
+    rb_cv_broken_memmem=no,
+    rb_cv_broken_memmem=yes,
+    rb_cv_broken_memmem=yes)
+])
+test x"$rb_cv_broken_memmem" = xyes && ac_cv_func_memmem=no
+
 AC_FUNC_FORK
 
 AC_CHECK_FUNCS(__syscall)
@@ -3882,40 +3909,6 @@ if test "${universal_binary-no}" = yes ; then
 		[rb_cv_architecture_available=yes], [rb_cv_architecture_available=no]))
 fi
 
-if test "$ac_cv_func_memmem" = yes; then
-  AC_CACHE_CHECK(for broken memmem, rb_cv_broken_memmem, [
-    AC_TRY_RUN([
-#include <string.h>
-
-int
-main()
-{
-  char *str = "hogefugafoobar";
-  char *rs = "foo";
-  char *empty = "";
-  char *p;
-
-  p = memmem(str, strlen(str), rs, strlen(rs));
-  if (p == str+8) {
-    p = memmem(str, strlen(str), empty, strlen(empty));
-    if (p == str)
-      return 0;
-    else
-      return 1;
-  }
-  else {
-    return 1;
-  }
-}
-    ],
-    rb_cv_broken_memmem=no,
-    rb_cv_broken_memmem=yes,
-    rb_cv_broken_memmem=yes)
-  ])
-  test x"$rb_cv_broken_memmem" = xyes && ac_cv_func_memmem=no
-fi
-
-
 CPPFLAGS="$CPPFLAGS "'$(DEFS)'
 test -z "$CPPFLAGS" || CPPFLAGS="$CPPFLAGS "; CPPFLAGS="$CPPFLAGS"'${cppflags}'
 if test -n "${cflags+set}"; then