diff --git a/lib/liby/main.c b/lib/liby/main.c
index 398f2ae53cef..c2955c407369 100644
--- a/lib/liby/main.c
+++ b/lib/liby/main.c
@@ -38,6 +38,10 @@ __FBSDID("$FreeBSD$");
 static char sccsid[] = "@(#)main.c	8.1 (Berkeley) 6/4/93";
 #endif /* not lint */
 
+#include <stdlib.h>
+
+int yyparse(void);
+
 int
 main(void)
 {