diff --git a/mach/pdp/cg/peep.c b/mach/pdp/cg/peep.c
index e78b10f22..32d0d040b 100644
--- a/mach/pdp/cg/peep.c
+++ b/mach/pdp/cg/peep.c
@@ -23,6 +23,7 @@ static char rcsid[] = "$Header$";
  */
 
 char buf[512];
+char *index();
 
 main() {
 	register n,sa;