diff --git a/util/byacc/main.c b/util/byacc/main.c
index 8b7935d1..32982239 100644
--- a/util/byacc/main.c
+++ b/util/byacc/main.c
@@ -70,6 +70,7 @@ int k;
 }
 
 
+void
 onintr()
 {
     done(1);