diff --git a/ChangeLog b/ChangeLog
index 7b5eb8681a..86d686ea02 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue Nov  8 14:50:55 2011  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* io.c (io_fwrite): call rb_w32_write_console() only if FMODE_TTY is
+	  set.  this is the one of the reason of IO writing slowness of Windows
+	  in 1.9.3 or later.
+
 Tue Nov  8 11:01:04 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* ext/pty/pty.c (get_device_once): FreeBSD's posix_openpt doesn't
diff --git a/io.c b/io.c
index 7996c06382..a2b96bad6b 100644
--- a/io.c
+++ b/io.c
@@ -1085,8 +1085,10 @@ static long
 io_fwrite(VALUE str, rb_io_t *fptr, int nosync)
 {
 #ifdef _WIN32
-    long len = rb_w32_write_console(str, fptr->fd);
-    if (len > 0) return len;
+    if (fptr->mode & FMODE_TTY) {
+	long len = rb_w32_write_console(str, fptr->fd);
+	if (len > 0) return len;
+    }
 #endif
     str = do_writeconv(str, fptr);
     return io_binwrite(str, RSTRING_PTR(str), RSTRING_LEN(str),