diff --git a/ChangeLog b/ChangeLog
index 016111311c..9c238d4e58 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Dec 14 02:05:42 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* io.c (rb_io_synchronized): should check if initialized.
+	  [ruby-dev:32585]
+
 Fri Dec 14 00:54:40 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* re.c (rb_reg_initialize): embedded string may override encoding
diff --git a/io.c b/io.c
index fdea5d2722..f0d314396b 100644
--- a/io.c
+++ b/io.c
@@ -3301,6 +3301,7 @@ pipe_finalize(rb_io_t *fptr, int noraise)
 void
 rb_io_synchronized(rb_io_t *fptr)
 {
+    rb_io_check_initialized(fptr);
     fptr->mode |= FMODE_SYNC;
 }