diff --git a/ChangeLog b/ChangeLog
index fe8fe2aaf8..23fffa8a04 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Dec 13 13:09:03 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* include/ruby/io.h (MakeOpenFile): fptr->enc should be
+	  intialized to zero.  [ruby-dev:32569]
+
 Thu Dec 13 08:56:01 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* io.c (rb_io_getc): use default external encoding if fptr->enc is
diff --git a/include/ruby/io.h b/include/ruby/io.h
index c2e0eaa2fc..5111592935 100644
--- a/include/ruby/io.h
+++ b/include/ruby/io.h
@@ -90,6 +90,7 @@ typedef struct rb_io_t {
     fp->rbuf_len = 0;\
     fp->rbuf_capa = 0;\
     fp->tied_io_for_writing = 0;\
+    fp->enc = 0;\
 } while (0)
 
 FILE *rb_io_stdio_file(rb_io_t *fptr);