diff --git a/ChangeLog b/ChangeLog
index f1fe4492a9..763a92eb60 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Sep 28 19:36:20 2009  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* win32/wini32.c (LK_ERR): with overlapped I/O, LockFileEx() returns
+	  ERROR_IO_PENDING if the file is locked.
+
 Mon Sep 28 19:05:05 2009  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* include/ruby/st.h: aligned prototype of st_hash_uint32 with function
diff --git a/win32/win32.c b/win32/win32.c
index 353873a22b..222af78c72 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -253,7 +253,7 @@ GetCurrentThreadHandle(void)
 	    i = 0;							\
 	else {								\
 	    DWORD err = GetLastError();					\
-	    if (err == ERROR_LOCK_VIOLATION)				\
+	    if (err == ERROR_LOCK_VIOLATION || err == ERROR_IO_PENDING)	\
 		errno = EWOULDBLOCK;					\
 	    else if (err == ERROR_NOT_LOCKED)				\
 		i = 0;							\