diff --git a/ietf/rtcp.h b/ietf/rtcp.h
index c7ae891..e6837a9 100644
--- a/ietf/rtcp.h
+++ b/ietf/rtcp.h
@@ -35,7 +35,7 @@ static inline void rtcp_set_rtp_version(uint8_t *p_rtcp)
     p_rtcp[0] = RTCP_RTP_VERSION << 6;
 }
 
-static inline uint8_t rtcp_get_rc(uint8_t *p_rtcp)
+static inline uint8_t rtcp_get_rc(const uint8_t *p_rtcp)
 {
     return p_rtcp[0] & 0x1f;
 }