diff --git a/event.c b/event.c
index 3e917fb9..c209213a 100644
--- a/event.c
+++ b/event.c
@@ -3314,7 +3314,7 @@ event_base_foreach_event(struct event_base *base,
 {
 	int r;
 	if ((!fn) || (!base)) {
-		return;
+		return -1;
 	}
 	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
 	r = event_base_foreach_event_nolock_(base, fn, arg);