diff --git a/include/libc.h b/include/libc.h
index 7024378d..ee396cc4 100644
--- a/include/libc.h
+++ b/include/libc.h
@@ -397,6 +397,8 @@ extern	void	p9syslog(int, char*, char*, ...);
 extern	long	p9time(long*);
 /* extern	int	tolower(int); <ctype.h> */
 /* extern	int	toupper(int); <ctype.h> */
+extern	void	needstack(int);
+
 #ifndef NOPLAN9DEFINES
 #define atexit		p9atexit
 #define atexitdont	p9atexitdont