diff --git a/ChangeLog b/ChangeLog
index 31661c9beb..ab53b27196 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Wed Jul 27 17:55:54 2011  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* include/ruby/missing.h: define __syscall if the platform has
+	  __syscall in the library but doesn't define it in headers
+	  for example Mac OS X.
+
 Wed Jul 27 15:39:14 2011  Eric Hodel  <drbrain@segment7.net>
 
 	* object.c:  Add usage documentation for BasicObject.  Based on patch
diff --git a/include/ruby/missing.h b/include/ruby/missing.h
index 067145a156..5309fe9466 100644
--- a/include/ruby/missing.h
+++ b/include/ruby/missing.h
@@ -51,6 +51,11 @@ struct timezone {
 };
 #endif
 
+#if defined(HAVE___SYSCALL) && !defined(__syscall)
+/* Mac OS X has __syscall but doen't defined in headers */
+off_t __syscall(quad_t number, ...);
+#endif
+
 #ifdef RUBY_EXPORT
 #undef RUBY_EXTERN
 #endif