diff --git a/ChangeLog b/ChangeLog
index 4da000a17e..73c1211332 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Feb  8 13:59:56 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* configure.in: revert r30725. Now we have proper runtime fallback.
+	  Therefore, no need compile time disabling. (see r30762).
+
 Tue Feb  8 01:00:21 2011  CHIKANAGA Tomoyuki  <nagachika00@gmail.com>
 
 	* process.c (proc_setgroups): add GC guard to prevent intermediate
diff --git a/configure.in b/configure.in
index 545bd7037c..0cf6536687 100644
--- a/configure.in
+++ b/configure.in
@@ -934,7 +934,6 @@ AS_CASE(["$target_os"],
 		fi
 		ac_cv_type_getgroups=gid_t # getgroups() on Rosetta fills garbage
 		ac_cv_lib_crypt_crypt=no
-		ac_cv_func_fdatasync=no # Mac OS 10.6 wrongly reports it has fdatasync
                 AC_CACHE_CHECK(for broken crypt with 8bit chars, rb_cv_broken_crypt,
                     [AC_TRY_RUN([
 #include <stdio.h>