diff --git a/src/libosmo-mgcp/mgcp_sdp.c b/src/libosmo-mgcp/mgcp_sdp.c
index f45d6e7..666b8c2 100644
--- a/src/libosmo-mgcp/mgcp_sdp.c
+++ b/src/libosmo-mgcp/mgcp_sdp.c
@@ -365,7 +365,7 @@
 
 	rc = msgb_printf(sdp,
 			 "v=0\r\n"
-			 "o=- %u 23 IN IP4 %s\r\n"
+			 "o=- %s 23 IN IP4 %s\r\n"
 			 "s=-\r\n"
 			 "c=IN IP4 %s\r\n"
 			 "t=0 0\r\n", conn->conn->id, addr, addr);