diff --git a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
index f73e73d..6f22f90 100644
--- a/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
+++ b/openbsc/src/osmo-bsc_mgcp/mgcp_main.c
@@ -158,8 +158,8 @@
 		perror("Gateway failed to read");
 		return -1;
 	} else if (slen > sizeof(addr)) {
-		fprintf(stderr, "Gateway received message from outerspace: %lu %lu\n",
-			(unsigned long int)slen, sizeof(addr));
+		fprintf(stderr, "Gateway received message from outerspace: %zu %zu\n",
+			slen, sizeof(addr));
 		return -1;
 	}