diff --git a/daemon/call.c b/daemon/call.c
index f4eb46359..71d656eb3 100644
--- a/daemon/call.c
+++ b/daemon/call.c
@@ -72,6 +72,7 @@ static void __call_free(call_t *p);
 static void __call_cleanup(call_t *c);
 static void __monologue_stop(struct call_monologue *ml);
 static void media_stop(struct call_media *m);
+__attribute__((nonnull(1, 2, 4)))
 static void __subscribe_medias_both_ways(struct call_media * a, struct call_media * b,
 		bool is_offer, medias_q *);
 
@@ -3398,9 +3399,6 @@ void __add_media_subscription(struct call_media * which, struct call_media * to,
 static void __subscribe_medias_both_ways(struct call_media * a, struct call_media * b,
 		bool is_offer, medias_q *medias)
 {
-	if (!a || !b)
-		return;
-
 	/* retrieve previous subscriptions to retain attributes */
 	struct media_subscription *a_ms = call_get_media_subscription(a->media_subscriptions_ht, b);
 	struct media_subscription *b_ms = call_get_media_subscription(b->media_subscriptions_ht, a);
diff --git a/include/call.h b/include/call.h
index 2384b7247..d40a8d988 100644
--- a/include/call.h
+++ b/include/call.h
@@ -825,6 +825,7 @@ void __monologue_free(struct call_monologue *m);
 void __monologue_tag(struct call_monologue *ml, const str *tag);
 void __monologue_viabranch(struct call_monologue *ml, const str *viabranch);
 struct packet_stream *__packet_stream_new(call_t *call);
+__attribute__((nonnull(1, 2)))
 void __add_media_subscription(struct call_media * which, struct call_media * to,
 		const struct sink_attrs *attrs);
 struct media_subscription *call_ml_get_top_ms(struct call_monologue *ml);