diff --git a/ChangeLog b/ChangeLog
index 457506ac74..ce37c52dd2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Jan 30 08:02:55 2011  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* configure.in: Mac OS X wrongly reports it has fdatasync(3).
+
 Sun Jan 30 03:29:47 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* ext/openssl/ossl_bn.c (GetBNPtr): add missing nil case.
diff --git a/configure.in b/configure.in
index 34af64062f..426fce5502 100644
--- a/configure.in
+++ b/configure.in
@@ -934,6 +934,7 @@ 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>