diff --git a/Shorewall-perl/Shorewall/Chains.pm b/Shorewall-perl/Shorewall/Chains.pm
index 29fc60481..2b2ff4680 100644
--- a/Shorewall-perl/Shorewall/Chains.pm
+++ b/Shorewall-perl/Shorewall/Chains.pm
@@ -1420,7 +1420,7 @@ sub do_helper( $ ) {
 sub do_length( $ ) {
     my $length = $_[0];
 
-    require_capability( 'LENGTH_MATCH' , 'Your kernel and/or iptables does not have length match support.' , '' );
+    require_capability( 'LENGTH_MATCH' , 'A Non-empty LENGTH' , 's' );
     $length ne '-' ? "-m length --length $length " : '';
 }