diff --git a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
index 5f703c2..1c03f27 100644
--- a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
+++ b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
@@ -156,7 +156,7 @@
 		return -1;
 	} else if (slen > sizeof(addr)) {
 		fprintf(stderr, "Gateway received message from outerspace: %zu %zu\n",
-			slen, sizeof(addr));
+			(size_t) slen, sizeof(addr));
 		return -1;
 	}