diff --git a/include/osmocom/mgcp/mgcp.h b/include/osmocom/mgcp/mgcp.h
index 1de579aaf..29963cc10 100644
--- a/include/osmocom/mgcp/mgcp.h
+++ b/include/osmocom/mgcp/mgcp.h
@@ -211,4 +211,4 @@ int mgcp_send_reset_all(struct mgcp_config *cfg);
 
 int mgcp_create_bind(const char *source_addr, struct osmo_fd *fd, int port, uint8_t dscp,
 		     uint8_t prio);
-int mgcp_udp_send(int fd, struct osmo_sockaddr *addr, int port, char *buf, int len);
+int mgcp_udp_send(int fd, struct osmo_sockaddr *addr, int port, const char *buf, int len);
diff --git a/src/libosmo-mgcp/mgcp_network.c b/src/libosmo-mgcp/mgcp_network.c
index abe01c949..e03c100a2 100644
--- a/src/libosmo-mgcp/mgcp_network.c
+++ b/src/libosmo-mgcp/mgcp_network.c
@@ -177,7 +177,7 @@ static uint32_t get_current_ts(unsigned codec_rate)
  *  \param[in] buf buffer that holds the data to be send.
  *  \param[in] len length of the data to be sent.
  *  \returns bytes sent, -1 on error. */
-int mgcp_udp_send(int fd, struct osmo_sockaddr *addr, int port, char *buf, int len)
+int mgcp_udp_send(int fd, struct osmo_sockaddr *addr, int port, const char *buf, int len)
 {
 	char ipbuf[INET6_ADDRSTRLEN];
 	size_t addr_len;