--- lib/Data/FormValidator/Results.pm.orig	2012-08-16 10:54:34.168443434 +0200
+++ lib/Data/FormValidator/Results.pm	2012-08-16 10:54:52.126443666 +0200
@@ -807,7 +807,7 @@
             # With methods, the value is the second argument
             my $val = $force_method_p ? $_[1] : $_[0];
             my ($match) = scalar ($val =~ $re);
-            if ($untaint_this && defined $match) {
+            if ($untaint_this && $match) {
                 # pass the value through a RE that matches anything to untaint it.
                 my ($untainted) = ($&  =~ m/(.*)/s);
                 return $untainted;
--- /dev/null	2012-06-14 10:53:10.614001004 +0200
+++ t/untaint_match_check.t	2012-08-16 10:57:38.747450934 +0200
@@ -0,0 +1,16 @@
+use strict;
+use warnings;
+use Test::More tests => 3;
+use Data::FormValidator;
+"unrelated match" =~ /match/;
+my $result = Data::FormValidator->check(
+    { a => 'invalid value' },    # input data
+    {                            # validation profile
+        untaint_all_constraints => 1,
+        optional                => ['a'],
+        constraints             => { a => qr/never matches/, },
+    },
+);
+ok( not $result->success ) or diag( 'Valid: ', $result->valid );
+ok( $result->has_invalid );
+is_deeply( scalar( $result->invalid ), { 'a' => [qr/never matches/] } );