diff --git a/usr.sbin/rpc.umntall/rpc.umntall.c b/usr.sbin/rpc.umntall/rpc.umntall.c
--- a/usr.sbin/rpc.umntall/rpc.umntall.c
+++ b/usr.sbin/rpc.umntall/rpc.umntall.c
@@ -261,7 +261,8 @@
 }
 
 static void
-usage() {
+usage(void)
+{
 	(void)fprintf(stderr, "%s\n",
 	    "usage: rpc.umntall [-kv] [-e expire] [-h host] [-p path]");
 	exit(1);