diff --git a/usr.sbin/jail/jaillex.l b/usr.sbin/jail/jaillex.l
index 157db9276b35..0a2fcd72a526 100644
--- a/usr.sbin/jail/jaillex.l
+++ b/usr.sbin/jail/jaillex.l
@@ -36,6 +36,7 @@ __FBSDID("$FreeBSD$");
 #include "jailp.h"
 #include "y.tab.h"
 
+#define YY_NO_INPUT
 #define YY_NO_UNPUT
 
 extern int yynerrs;