diff --git a/src/libosmo-mgcp-client/mgcp_client.c b/src/libosmo-mgcp-client/mgcp_client.c
index 55ce7b2..8e6780e 100644
--- a/src/libosmo-mgcp-client/mgcp_client.c
+++ b/src/libosmo-mgcp-client/mgcp_client.c
@@ -1105,30 +1105,40 @@
 	const char *codec;
 	unsigned int pt;
 
-	rc += msgb_printf(msg, "L:");
+	rc |= msgb_printf(msg, "L:");
 
 	if (mgcp_msg->ptime)
-		rc += msgb_printf(msg, " p:%u,", mgcp_msg->ptime);
+		rc |= msgb_printf(msg, " p:%u,", mgcp_msg->ptime);
 
 	if (mgcp_msg->codecs_len) {
-		rc += msgb_printf(msg, " a:");
+		rc |= msgb_printf(msg, " a:");
 		for (i = 0; i < mgcp_msg->codecs_len; i++) {
 			pt = mgcp_msg->codecs[i];
 			codec = get_value_string_or_null(osmo_mgcpc_codec_names, pt);
 
 			/* Note: Use codec descriptors from enum mgcp_codecs
 			 * in mgcp_client only! */
-			OSMO_ASSERT(codec);
-			rc += msgb_printf(msg, "%s", extract_codec_name(codec));
+			if (!codec) {
+				msgb_free(msg);
+				return -EINVAL;
+			}
+
+			rc |= msgb_printf(msg, "%s", extract_codec_name(codec));
 			if (i < mgcp_msg->codecs_len - 1)
-				rc += msgb_printf(msg, ";");
+				rc |= msgb_printf(msg, ";");
 		}
-		rc += msgb_printf(msg, ",");
+		rc |= msgb_printf(msg, ",");
 	}
 
-	rc += msgb_printf(msg, " nt:IN\r\n");
+	rc |= msgb_printf(msg, " nt:IN\r\n");
 
-	return rc;
+	if (rc != 0) {
+		LOGP(DLMGCP, LOGL_ERROR,
+		     "message buffer to small, can not generate MGCP message (LCO)\n");
+		msgb_free(msg);
+		return -ENOBUFS;
+	}
+	return 0;
 }
 
 /* Helper function for mgcp_msg_gen(): Add SDP information to MGCP message */
@@ -1142,64 +1152,64 @@
 	unsigned int pt;
 
 	/* Add separator to mark the beginning of the SDP block */
-	rc += msgb_printf(msg, "\r\n");
+	rc |= msgb_printf(msg, "\r\n");
 
 	/* Add SDP protocol version */
-	rc += msgb_printf(msg, "v=0\r\n");
+	rc |= msgb_printf(msg, "v=0\r\n");
 
 	/* Determine local IP-Address */
 	if (osmo_sock_local_ip(local_ip, mgcp->actual.remote_addr) < 0) {
 		LOGP(DLMGCP, LOGL_ERROR,
 		     "Could not determine local IP-Address!\n");
 		msgb_free(msg);
-		return -2;
+		return -EINVAL;
 	}
 	local_ip_family = osmo_ip_str_type(local_ip);
 	if (local_ip_family == AF_UNSPEC) {
 		msgb_free(msg);
-		return -2;
+		return -EINVAL;
 	}
 	audio_ip_family = osmo_ip_str_type(mgcp_msg->audio_ip);
 	if (audio_ip_family == AF_UNSPEC) {
 		msgb_free(msg);
-		return -2;
+		return -EINVAL;
 	}
 
 	/* Add owner/creator (SDP) */
-	rc += msgb_printf(msg, "o=- %x 23 IN IP%c %s\r\n", mgcp_msg->call_id,
+	rc |= msgb_printf(msg, "o=- %x 23 IN IP%c %s\r\n", mgcp_msg->call_id,
 			  local_ip_family == AF_INET6 ? '6' : '4',
 			  local_ip);
 
 	/* Add session name (none) */
-	rc += msgb_printf(msg, "s=-\r\n");
+	rc |= msgb_printf(msg, "s=-\r\n");
 
 	/* Add RTP address and port */
 	if (mgcp_msg->audio_port == 0) {
 		LOGP(DLMGCP, LOGL_ERROR,
 		     "Invalid port number, can not generate MGCP message\n");
 		msgb_free(msg);
-		return -2;
+		return -EINVAL;
 	}
 	if (strlen(mgcp_msg->audio_ip) <= 0) {
 		LOGP(DLMGCP, LOGL_ERROR,
 		     "Empty ip address, can not generate MGCP message\n");
 		msgb_free(msg);
-		return -2;
+		return -EINVAL;
 	}
-	rc += msgb_printf(msg, "c=IN IP%c %s\r\n",
+	rc |= msgb_printf(msg, "c=IN IP%c %s\r\n",
 			  audio_ip_family == AF_INET6 ? '6' : '4',
 			  mgcp_msg->audio_ip);
 
 	/* Add time description, active time (SDP) */
-	rc += msgb_printf(msg, "t=0 0\r\n");
+	rc |= msgb_printf(msg, "t=0 0\r\n");
 
-	rc += msgb_printf(msg, "m=audio %u RTP/AVP", mgcp_msg->audio_port);
+	rc |= msgb_printf(msg, "m=audio %u RTP/AVP", mgcp_msg->audio_port);
 	for (i = 0; i < mgcp_msg->codecs_len; i++) {
 		pt = map_codec_to_pt(mgcp_msg->ptmap, mgcp_msg->ptmap_len, mgcp_msg->codecs[i]);
-		rc += msgb_printf(msg, " %u", pt);
+		rc |= msgb_printf(msg, " %u", pt);
 
 	}
-	rc += msgb_printf(msg, "\r\n");
+	rc |= msgb_printf(msg, "\r\n");
 
 	/* Add optional codec parameters (fmtp) */
 	if (mgcp_msg->param_present) {
@@ -1209,9 +1219,9 @@
 				   continue;
 			pt = map_codec_to_pt(mgcp_msg->ptmap, mgcp_msg->ptmap_len, mgcp_msg->codecs[i]);
 			if (mgcp_msg->param.amr_octet_aligned_present && mgcp_msg->param.amr_octet_aligned)
-				rc += msgb_printf(msg, "a=fmtp:%u octet-align=1\r\n", pt);
+				rc |= msgb_printf(msg, "a=fmtp:%u octet-align=1\r\n", pt);
 			else if (mgcp_msg->param.amr_octet_aligned_present && !mgcp_msg->param.amr_octet_aligned)
-				rc += msgb_printf(msg, "a=fmtp:%u octet-align=0\r\n", pt);
+				rc |= msgb_printf(msg, "a=fmtp:%u octet-align=0\r\n", pt);
 		}
 	}
 
@@ -1226,16 +1236,26 @@
 
 			/* Note: Use codec descriptors from enum mgcp_codecs
 			 * in mgcp_client only! */
-			OSMO_ASSERT(codec);
+			if (!codec) {
+				msgb_free(msg);
+				return -EINVAL;
+			}
 
-			rc += msgb_printf(msg, "a=rtpmap:%u %s\r\n", pt, codec);
+			rc |= msgb_printf(msg, "a=rtpmap:%u %s\r\n", pt, codec);
 		}
 	}
 
 	if (mgcp_msg->ptime)
-		rc += msgb_printf(msg, "a=ptime:%u\r\n", mgcp_msg->ptime);
+		rc |= msgb_printf(msg, "a=ptime:%u\r\n", mgcp_msg->ptime);
 
-	return rc;
+	if (rc != 0) {
+		LOGP(DLMGCP, LOGL_ERROR,
+		     "message buffer to small, can not generate MGCP message (SDP)\n");
+		msgb_free(msg);
+		return -ENOBUFS;
+	}
+
+	return 0;
 }
 
 /*! Generate an MGCP message
@@ -1248,7 +1268,6 @@
 	uint32_t mandatory_mask;
 	struct msgb *msg = msgb_alloc_headroom(4096, 128, "MGCP tx");
 	int rc = 0;
-	int rc_sdp;
 	bool use_sdp = false;
 	char buf[32];
 
@@ -1259,23 +1278,23 @@
 	switch (mgcp_msg->verb) {
 	case MGCP_VERB_CRCX:
 		mandatory_mask = MGCP_CRCX_MANDATORY;
-		rc += msgb_printf(msg, "CRCX %u", trans_id);
+		rc |= msgb_printf(msg, "CRCX %u", trans_id);
 		break;
 	case MGCP_VERB_MDCX:
 		mandatory_mask = MGCP_MDCX_MANDATORY;
-		rc += msgb_printf(msg, "MDCX %u", trans_id);
+		rc |= msgb_printf(msg, "MDCX %u", trans_id);
 		break;
 	case MGCP_VERB_DLCX:
 		mandatory_mask = MGCP_DLCX_MANDATORY;
-		rc += msgb_printf(msg, "DLCX %u", trans_id);
+		rc |= msgb_printf(msg, "DLCX %u", trans_id);
 		break;
 	case MGCP_VERB_AUEP:
 		mandatory_mask = MGCP_AUEP_MANDATORY;
-		rc += msgb_printf(msg, "AUEP %u", trans_id);
+		rc |= msgb_printf(msg, "AUEP %u", trans_id);
 		break;
 	case MGCP_VERB_RSIP:
 		mandatory_mask = MGCP_RSIP_MANDATORY;
-		rc += msgb_printf(msg, "RSIP %u", trans_id);
+		rc |= msgb_printf(msg, "RSIP %u", trans_id);
 		break;
 	default:
 		LOGP(DLMGCP, LOGL_ERROR,
@@ -1309,15 +1328,15 @@
 			return NULL;
 		}
 
-		rc += msgb_printf(msg, " %s", mgcp_msg->endpoint);
+		rc |= msgb_printf(msg, " %s", mgcp_msg->endpoint);
 	}
 
 	/* Add protocol version */
-	rc += msgb_printf(msg, " MGCP 1.0\r\n");
+	rc |= msgb_printf(msg, " MGCP 1.0\r\n");
 
 	/* Add call id */
 	if (mgcp_msg->presence & MGCP_MSG_PRESENCE_CALL_ID)
-		rc += msgb_printf(msg, "C: %x\r\n", mgcp_msg->call_id);
+		rc |= msgb_printf(msg, "C: %x\r\n", mgcp_msg->call_id);
 
 	/* Add connection id */
 	if (mgcp_msg->presence & MGCP_MSG_PRESENCE_CONN_ID) {
@@ -1327,7 +1346,7 @@
 			msgb_free(msg);
 			return NULL;
 		}
-		rc += msgb_printf(msg, "I: %s\r\n", mgcp_msg->conn_id);
+		rc |= msgb_printf(msg, "I: %s\r\n", mgcp_msg->conn_id);
 	}
 
 	/* Using SDP makes sense when a valid IP/Port combination is specifiec,
@@ -1339,19 +1358,21 @@
 	/* Add local connection options (LCO) */
 	if (!use_sdp
 	    && (mgcp_msg->verb == MGCP_VERB_CRCX
-		|| mgcp_msg->verb == MGCP_VERB_MDCX))
-		rc += add_lco(msg, mgcp_msg);
+		|| mgcp_msg->verb == MGCP_VERB_MDCX)) {
+	        if (add_lco(msg, mgcp_msg) < 0)
+			return NULL;
+	}
 
 	/* Add mode */
 	if (mgcp_msg->presence & MGCP_MSG_PRESENCE_CONN_MODE)
-		rc +=
+		rc |=
 		    msgb_printf(msg, "M: %s\r\n",
 				mgcp_client_cmode_name(mgcp_msg->conn_mode));
 
 	/* Add X-Osmo-IGN */
 	if ((mgcp_msg->presence & MGCP_MSG_PRESENCE_X_OSMO_IGN)
 	    && (mgcp_msg->x_osmo_ign != 0))
-		rc +=
+		rc |=
 		    msgb_printf(msg, MGCP_X_OSMO_IGN_HEADER "%s\r\n",
 				mgcp_msg->x_osmo_ign & MGCP_X_OSMO_IGN_CALLID ? " C": "");
 
@@ -1365,7 +1386,7 @@
 			return NULL;
 		}
 		snprintf(buf, sizeof(buf), " %d", mgcp_msg->x_osmo_osmux_cid);
-		rc +=
+		rc |=
 		    msgb_printf(msg, MGCP_X_OSMO_OSMUX_HEADER "%s\r\n",
 				mgcp_msg->x_osmo_osmux_cid == -1 ? " *": buf);
 	}
@@ -1375,10 +1396,8 @@
 	if (use_sdp
 	    && (mgcp_msg->verb == MGCP_VERB_CRCX
 		|| mgcp_msg->verb == MGCP_VERB_MDCX)) {
-		rc_sdp = add_sdp(msg, mgcp_msg, mgcp);
-		if (rc_sdp == -2)
+	        if (add_sdp(msg, mgcp_msg, mgcp) < 0)
 			return NULL;
-		rc += rc_sdp;
 	}
 
 	if (rc != 0) {
diff --git a/tests/mgcp_client/mgcp_client_test.err b/tests/mgcp_client/mgcp_client_test.err
index ac13f03..80119cb 100644
--- a/tests/mgcp_client/mgcp_client_test.err
+++ b/tests/mgcp_client/mgcp_client_test.err
@@ -1,5 +1,5 @@
 DLMGCP MGCP client: using endpoint domain '@mgw'
-DLMGCP message buffer to small, can not generate MGCP message
+DLMGCP message buffer to small, can not generate MGCP message (SDP)
 
 test_mgcp_client_cancel():
 DLMGCP MGCP client: using endpoint domain '@mgw'