diff --git a/include/osmocom/mgcp/mgcp_codec.h b/include/osmocom/mgcp/mgcp_codec.h
index 2bbb86e..3ead60a 100644
--- a/include/osmocom/mgcp/mgcp_codec.h
+++ b/include/osmocom/mgcp/mgcp_codec.h
@@ -2,6 +2,6 @@
 
 void mgcp_codec_summary(struct mgcp_conn_rtp *conn);
 void mgcp_codec_reset_all(struct mgcp_conn_rtp *conn);
-int mgcp_codec_add(struct mgcp_conn_rtp *conn, int payload_type, const char *audio_name, struct mgcp_codec_param *param);
+int mgcp_codec_add(struct mgcp_conn_rtp *conn, int payload_type, const char *audio_name, const struct mgcp_codec_param *param);
 int mgcp_codec_decide(struct mgcp_conn_rtp *conn);
 int mgcp_codec_pt_translate(struct mgcp_conn_rtp *conn_src, struct mgcp_conn_rtp *conn_dst, int payload_type);
diff --git a/src/libosmo-mgcp/mgcp_codec.c b/src/libosmo-mgcp/mgcp_codec.c
index e9e2c62..d5b99e8 100644
--- a/src/libosmo-mgcp/mgcp_codec.c
+++ b/src/libosmo-mgcp/mgcp_codec.c
@@ -101,7 +101,7 @@
 
 /* Set members of struct mgcp_rtp_codec, extrapolate in missing information. Param audio_name is expected in uppercase. */
 static int codec_set(void *ctx, struct mgcp_rtp_codec *codec, int payload_type, const char *audio_name,
-		     unsigned int pt_offset, struct mgcp_codec_param *param)
+		     unsigned int pt_offset, const struct mgcp_codec_param *param)
 {
 	int rate;
 	int channels;
@@ -242,7 +242,7 @@
  *  \param[in] audio_name audio codec name, in uppercase (e.g. "GSM/8000/1").
  *  \param[in] param optional codec parameters (set to NULL when unused).
  *  \returns 0 on success, -EINVAL on failure. */
-int mgcp_codec_add(struct mgcp_conn_rtp *conn, int payload_type, const char *audio_name, struct mgcp_codec_param *param)
+int mgcp_codec_add(struct mgcp_conn_rtp *conn, int payload_type, const char *audio_name, const struct mgcp_codec_param *param)
 {
 	int rc;