diff --git a/ChangeLog b/ChangeLog
index 9671458563..66ebc3ae23 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Dec 23 15:30:02 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* io.c (pipe_open): need to initialize args.
+
 Tue Dec 23 14:18:14 2008  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* include/ruby/st.h: need to include defines.h because LONG_LONG is
diff --git a/io.c b/io.c
index da1e5c1405..632e3500c9 100644
--- a/io.c
+++ b/io.c
@@ -4448,7 +4448,7 @@ pipe_open(struct rb_exec_arg *eargp, VALUE prog, const char *modestr, int fmode,
     struct popen_arg arg;
 #elif defined(_WIN32)
     volatile VALUE argbuf;
-    char **args;
+    char **args = NULL;
     struct rb_exec_arg sarg;
     int pair[2], write_pair[2];
 #endif