diff --git a/Shorewall/Perl/Shorewall/Chains.pm b/Shorewall/Perl/Shorewall/Chains.pm
index 631cd0c39..1f0ca977c 100644
--- a/Shorewall/Perl/Shorewall/Chains.pm
+++ b/Shorewall/Perl/Shorewall/Chains.pm
@@ -4376,7 +4376,7 @@ sub do_iproto( $$$ )
 			    }
 
 			    $ports = validate_port_list $pname , $ports;
-			    push @output, multiport => ( $srcndst ? "-m multiport ${invert}--ports ${ports} " : "-m multiport ${invert}--dports ${ports} " );
+			    push @output, multiport => ( $srcndst ? "${invert}--ports ${ports} " : "${invert}--dports ${ports} " );
 			    $multiport = 1;
 			}  else {
 			    fatal_error "Missing DEST PORT" unless supplied $ports;
diff --git a/Shorewall/Perl/Shorewall/Providers.pm b/Shorewall/Perl/Shorewall/Providers.pm
index 45e72d2d4..f12050b24 100644
--- a/Shorewall/Perl/Shorewall/Providers.pm
+++ b/Shorewall/Perl/Shorewall/Providers.pm
@@ -228,6 +228,7 @@ sub copy_and_edit_table( $$$$ ) {
     #
     for ( split ',', $copy ) {
 	unless ( $copied{$_} ) {
+	    fatal_error "Unknown interface ($_)" unless known_interface($_);
 	    push @copy, $_;
 	    $copied{$_} = 1;
 	}