diff --git a/daemon/codec.c b/daemon/codec.c
index 6bccca6b9..5b76d01d0 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -4746,6 +4746,7 @@ static void codec_store_find_matching_codecs(GQueue *out_compat, struct rtp_payl
 	}
 }
 
+__attribute__((nonnull(1, 2)))
 static void codec_store_add_raw_link(struct codec_store *cs, struct rtp_payload_type *pt, GList *link) {
 	// cs->media may be NULL
 	ensure_codec_def(pt, cs->media);
@@ -4768,14 +4769,17 @@ static void codec_store_add_raw_link(struct codec_store *cs, struct rtp_payload_
 }
 
 // appends to the end, but before supplemental codecs
+__attribute__((nonnull(1, 2)))
 static void codec_store_add_raw_order(struct codec_store *cs, struct rtp_payload_type *pt) {
 	codec_store_add_raw_link(cs, pt, cs->supp_link);
 }
 // appends to the end
+__attribute__((nonnull(1, 2)))
 void codec_store_add_raw(struct codec_store *cs, struct rtp_payload_type *pt) {
 	codec_store_add_raw_link(cs, pt, NULL);
 }
 
+__attribute__((nonnull(1, 2)))
 static struct rtp_payload_type *codec_store_add_link(struct codec_store *cs,
 		struct rtp_payload_type *pt, GList *link)
 {
@@ -5065,7 +5069,7 @@ int codec_store_accept_one(struct codec_store *cs, GQueue *accept, bool accept_a
 
 	struct rtp_payload_type *accept_pt = NULL;
 
-	for (GList *l = accept ? accept->head : NULL; l; l = l->next) {
+	for (GList *l = accept->head; l; l = l->next) {
 		// iterate through list and look for the first supported codec
 		str *codec = l->data;
 		if (!str_cmp(codec, "any")) {
@@ -5234,7 +5238,7 @@ void codec_store_answer(struct codec_store *dst, struct codec_store *src, struct
 	// populate dst via output PTs from src's codec handlers
 	for (GList *l = src->codec_prefs.head; l; l = l->next) {
 		bool add_codec = true;
-		if (flags && flags->single_codec && num_codecs >= 1)
+		if (flags->single_codec && num_codecs >= 1)
 			add_codec = false;
 
 		struct rtp_payload_type *pt = l->data;
diff --git a/include/codec.h b/include/codec.h
index a26d4aa2e..ca32de089 100644
--- a/include/codec.h
+++ b/include/codec.h
@@ -116,24 +116,39 @@ struct codec_store_args {
 	bool answer_only;
 };
 
+__attribute__((nonnull(1)))
 void codec_store_cleanup(struct codec_store *cs);
+__attribute__((nonnull(1)))
 void codec_store_init(struct codec_store *cs, struct call_media *);
+__attribute__((nonnull(1, 2)))
 void __codec_store_populate(struct codec_store *dst, struct codec_store *src, struct codec_store_args);
 #define codec_store_populate(dst, src, ...) \
 	__codec_store_populate(dst, src, (struct codec_store_args) {__VA_ARGS__})
+__attribute__((nonnull(1, 2)))
 void __codec_store_populate_reuse(struct codec_store *, struct codec_store *, struct codec_store_args);
 #define codec_store_populate_reuse(dst, src, ...) \
 	__codec_store_populate_reuse(dst, src, (struct codec_store_args) {__VA_ARGS__})
+__attribute__((nonnull(1, 2)))
 void codec_store_add_raw(struct codec_store *cs, struct rtp_payload_type *pt);
+__attribute__((nonnull(1, 2)))
 void codec_store_strip(struct codec_store *, GQueue *strip, GHashTable *except);
+__attribute__((nonnull(1, 2, 3)))
 void codec_store_offer(struct codec_store *, GQueue *, struct codec_store *);
+__attribute__((nonnull(1, 2)))
 void codec_store_check_empty(struct codec_store *, struct codec_store *);
+__attribute__((nonnull(1, 2)))
 void codec_store_accept(struct codec_store *, GQueue *, struct codec_store *);
+__attribute__((nonnull(1, 2)))
 int codec_store_accept_one(struct codec_store *, GQueue *, bool accept_any);
+__attribute__((nonnull(1, 2)))
 void codec_store_track(struct codec_store *, GQueue *);
+__attribute__((nonnull(1, 2, 3)))
 void codec_store_transcode(struct codec_store *, GQueue *, struct codec_store *);
+__attribute__((nonnull(1, 2, 3)))
 void codec_store_answer(struct codec_store *dst, struct codec_store *src, struct sdp_ng_flags *flags);
+__attribute__((nonnull(1, 2)))
 void codec_store_synthesise(struct codec_store *dst, struct codec_store *opposite);
+__attribute__((nonnull(1, 2)))
 bool codec_store_is_full_answer(const struct codec_store *src, const struct codec_store *dst);
 
 void codec_add_raw_packet(struct media_packet *mp, unsigned int clockrate);