--- src/lib/libc/stdio/vfprintf.c	2005/11/20 11:07:30	1.14
+++ src/lib/libc/stdio/vfprintf.c	2006/03/02 18:05:30	1.15
@@ -159,6 +159,7 @@ __sbprintf(FILE *fp, const char *fmt, va
 	fake.fl_mutex = fp->fl_mutex;
 	fake.fl_owner = fp->fl_owner;
 	fake.fl_count = fp->fl_count;
+	memset(WCIO_GET(&fake), 0, sizeof(struct wchar_io_data));
 
 	/* set up the buffer */
 	fake._bf._base = fake.pub._p = buf;