diff --git a/ChangeLog b/ChangeLog
index 15f2e0531b..96c48f107c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Aug 18 14:22:45 2013  Tanaka Akira  <akr@fsij.org>
+
+	* configure.in: Revert r42604.  It causes linking librt on systems
+	  with newer glibc uselessly.
+
 Sun Aug 18 13:18:38 2013  Tanaka Akira  <akr@fsij.org>
 
 	* process.c (Init_process): Add constants: CLOCK_REALTIME_COARSE,
diff --git a/configure.in b/configure.in
index d1a42d9eb8..62aaf72f5f 100644
--- a/configure.in
+++ b/configure.in
@@ -1748,6 +1748,7 @@ AC_CHECK_FUNCS(_setjmp)			# used for AC_ARG_WITH(setjmp-type)
 AC_CHECK_FUNCS(_setjmpex)		# used for AC_ARG_WITH(setjmp-type)
 AC_CHECK_FUNCS(chroot)
 AC_CHECK_FUNCS(chsize)
+AC_CHECK_FUNCS(clock_gettime)
 AC_CHECK_FUNCS(cosh)
 AC_CHECK_FUNCS(daemon)
 AC_CHECK_FUNCS(dl_iterate_phdr)
@@ -1855,13 +1856,13 @@ RUBY_CHECK_BUILTIN_FUNC(__builtin_clzl, [__builtin_clzl(0)])
 RUBY_CHECK_BUILTIN_FUNC(__builtin_clzll, [__builtin_clzll(0)])
 
 # Some platform need -lrt for clock_gettime, but the other don't.
-AC_CHECK_LIB(rt, clock_gettime)
-if test x"$ac_cv_lib_rt_clock_gettime" = xyes; then
+if test x"$ac_cv_func_clock_gettime" != xyes; then
     # glibc 2.17 moves clock_* functions from librt to the main C library.
     # http://sourceware.org/ml/libc-announce/2012/msg00001.html
-    ac_cv_func_clock_gettime="$ac_cv_lib_rt_clock_gettime"
+    AC_CHECK_LIB(rt, clock_gettime)
+    unset ac_cv_func_clock_gettime
+    AC_CHECK_FUNCS(clock_gettime)
 fi
-AC_CHECK_FUNCS(clock_gettime)
 
 AC_CACHE_CHECK(for unsetenv returns a value, rb_cv_unsetenv_return_value,
   [AC_TRY_COMPILE([