diff --git a/utils/osmo-auc-gen.c b/utils/osmo-auc-gen.c
index 72f1fcd..e3e1b43 100644
--- a/utils/osmo-auc-gen.c
+++ b/utils/osmo-auc-gen.c
@@ -85,7 +85,7 @@
 	.algo = OSMO_AUTH_ALG_NONE,
 };
 
-static void help()
+static void help(void)
 {
 	int alg;
 	printf( "-2  --2g\tUse 2G (GSM) authentication\n"