diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index 89e207a..d34aff1 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -1676,7 +1676,7 @@
 
 	if (hostent->h_length != sizeof(struct in_addr)) {
 		LOGMMCTXP(LOGL_ERROR, lookup->mmctx,
-			"Wrong addr size(%d)\n", sizeof(struct in_addr));
+			"Wrong addr size(%zu)\n", sizeof(struct in_addr));
 		goto reject_due_failure;
 	}