diff --git a/sbin/reboot/reboot.c b/sbin/reboot/reboot.c
index 0a9ac51046c2..1124ec6b6e08 100644
--- a/sbin/reboot/reboot.c
+++ b/sbin/reboot/reboot.c
@@ -231,7 +231,7 @@ usage(void)
 }
 
 static u_int
-get_pageins()
+get_pageins(void)
 {
 	u_int pageins;
 	size_t len;