diff --git a/daemon/codec.c b/daemon/codec.c
index 43bcab2c00..aac6fa2bd9 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -4732,7 +4732,7 @@ static void codec_store_find_matching_codecs(GQueue *out_compat, struct rtp_payl
 		ensure_codec_def(pt2, cs->media);
 		int match;
 		if (pt)
-			match = rtp_payload_type_fmt_eq(pt, pt2);
+			match = rtp_payload_type_fmt_cmp(pt, pt2);
 		else
 			match = (str_cmp_str(codec, &pt2->encoding) == 0) ? 0 : -1;
 		if (match == 0) {
diff --git a/lib/rtplib.c b/lib/rtplib.c
index fbfda7a152..f1b3b89215 100644
--- a/lib/rtplib.c
+++ b/lib/rtplib.c
@@ -145,6 +145,7 @@ const struct rtp_payload_type *rtp_get_rfc_codec(const str *codec) {
 }
 
 // helper function: matches only basic params, without matching payload type number
+__attribute__((nonnull(1, 2)))
 static bool rtp_payload_type_fmt_eq_nf(const struct rtp_payload_type *a, const struct rtp_payload_type *b) {
 	if (a->clock_rate != b->clock_rate)
 		return false;
@@ -157,7 +158,7 @@ static bool rtp_payload_type_fmt_eq_nf(const struct rtp_payload_type *a, const s
 
 // matches basic params and format params, but not payload type number
 // returns matching val as per format_cmp_f
-int rtp_payload_type_fmt_eq(const struct rtp_payload_type *a, const struct rtp_payload_type *b) {
+int rtp_payload_type_fmt_cmp(const struct rtp_payload_type *a, const struct rtp_payload_type *b) {
 	if (!rtp_payload_type_fmt_eq_nf(a, b))
 		return -1;
 	if (a->codec_def && a->codec_def == b->codec_def) {
@@ -171,21 +172,21 @@ int rtp_payload_type_fmt_eq(const struct rtp_payload_type *a, const struct rtp_p
 	return 0;
 }
 bool rtp_payload_type_fmt_eq_exact(const struct rtp_payload_type *a, const struct rtp_payload_type *b) {
-	return rtp_payload_type_fmt_eq(a, b) == 0;
+	return rtp_payload_type_fmt_cmp(a, b) == 0;
 }
 bool rtp_payload_type_fmt_eq_compat(const struct rtp_payload_type *a, const struct rtp_payload_type *b) {
-	return rtp_payload_type_fmt_eq(a, b) >= 0;
+	return rtp_payload_type_fmt_cmp(a, b) >= 0;
 }
 
 bool rtp_payload_type_eq_exact(const struct rtp_payload_type *a, const struct rtp_payload_type *b) {
 	if (a->payload_type != b->payload_type)
 		return false;
-	return rtp_payload_type_fmt_eq(a, b) == 0;
+	return rtp_payload_type_fmt_cmp(a, b) == 0;
 }
 bool rtp_payload_type_eq_compat(const struct rtp_payload_type *a, const struct rtp_payload_type *b) {
 	if (a->payload_type != b->payload_type)
 		return false;
-	return rtp_payload_type_fmt_eq(a, b) >= 0;
+	return rtp_payload_type_fmt_cmp(a, b) >= 0;
 }
 
 // same as rtp_payload_type_fmt_eq_nf plus matching payload type number
diff --git a/lib/rtplib.h b/lib/rtplib.h
index 8325efa12b..fa02a084e8 100644
--- a/lib/rtplib.h
+++ b/lib/rtplib.h
@@ -125,13 +125,19 @@ const struct rtp_payload_type *rtp_get_rfc_codec(const str *codec);
 
 // if not `exact` then also returns true if `a` is compatible with `b`
 // matches all params
+__attribute__((nonnull(1, 2)))
 bool rtp_payload_type_eq_exact(const struct rtp_payload_type *a, const struct rtp_payload_type *b);
+__attribute__((nonnull(1, 2)))
 bool rtp_payload_type_eq_compat(const struct rtp_payload_type *a, const struct rtp_payload_type *b);
 // matches only basic params and payload type number
+__attribute__((nonnull(1, 2)))
 bool rtp_payload_type_eq_nf(const struct rtp_payload_type *, const struct rtp_payload_type *);
 // matches all params except payload type number
-int rtp_payload_type_fmt_eq(const struct rtp_payload_type *a, const struct rtp_payload_type *b);
+__attribute__((nonnull(1, 2)))
+int rtp_payload_type_fmt_cmp(const struct rtp_payload_type *a, const struct rtp_payload_type *b);
+__attribute__((nonnull(1, 2)))
 bool rtp_payload_type_fmt_eq_exact(const struct rtp_payload_type *a, const struct rtp_payload_type *b);
+__attribute__((nonnull(1, 2)))
 bool rtp_payload_type_fmt_eq_compat(const struct rtp_payload_type *a, const struct rtp_payload_type *b);