diff --git a/ChangeLog b/ChangeLog
index c610a22a99..cbee596033 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Nov  2 14:54:02 2004  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* io.c (pipe_open): need to set cmd if argc == 0 (win32).
+
 Tue Nov  2 01:20:09 2004  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* io.c (pipe_open): IO.popen should take array as 1st argument for
diff --git a/io.c b/io.c
index 1b5e7acfa9..0dbb6b741c 100644
--- a/io.c
+++ b/io.c
@@ -2852,6 +2852,9 @@ pipe_open(argc, argv, mode)
 	rb_w32_join_argv(cmd, args);
 	exename = RSTRING(prog)->ptr;
     }
+    else {
+	cmd = StringValueCStr(prog);
+    }
     while ((pid = rb_w32_pipe_exec(cmd, exename, openmode, &fpr, &fpw)) == -1) {
 	/* exec failed */
 	switch (errno) {