diff --git a/Shorewall/Perl/Shorewall/Config.pm b/Shorewall/Perl/Shorewall/Config.pm
index 130051d0e..c8792e6fc 100644
--- a/Shorewall/Perl/Shorewall/Config.pm
+++ b/Shorewall/Perl/Shorewall/Config.pm
@@ -735,11 +735,13 @@ sub assert( $ ) {
 # Convert value to decimal number
 #
 sub numeric_value ( $ ) {
-    no warnings;
     my $mark = lc $_[0];
-    return undef unless $mark =~ /^-?(0x[a-f0-9]+|0[0-7]*|[1-9]\d*)$/;
-    $mark =~ /^0/ ? oct $mark : $mark;
+    my $negative = ( $mark =~ s/^-// );
+    return undef unless $mark =~ /^(0x[a-f0-9]+|0[0-7]*|[1-9]\d*)$/;
+    no warnings;
+    $mark = ( $mark =~ /^0/ ? oct $mark : $mark );
     use warnings;
+    $negative ? - $mark : $mark;
 }
 
 sub numeric_value1 ( $ ) {
diff --git a/Shorewall/Perl/Shorewall/Tc.pm b/Shorewall/Perl/Shorewall/Tc.pm
index beb96bb81..867bada9e 100644
--- a/Shorewall/Perl/Shorewall/Tc.pm
+++ b/Shorewall/Perl/Shorewall/Tc.pm
@@ -316,14 +316,12 @@ sub process_tc_rule( $$$$$$$$$$$$ ) {
 
 			    if ( defined $m1 && $m1 ne '' ) {
 				$val = numeric_value ($m1);
-				fatal_error "Invalid Mask ($m1)" if $m1 =~ /^-0x/;
 				fatal_error "Invalid Mask ($m1)" unless defined $val && $val && $val <= 0xffffffff;
 				$mask1 = $m1;
 			    }
 
 			    if ( defined $m2 && $m2 ne '' ) {
 				$val = numeric_value ($m2);
-				fatal_error "Invalid Mask ($m2)" if $m2 =~ /^-0x/;
 				fatal_error "Invalid Mask ($m2)" unless defined $val && $val <= 0xffffffff;
 				$mask2 = $m2;
 			    }