--- /dev/null
+#!perl -Tw
+
+use warnings;
+use strict;
+use Test::More tests => 4;
+use HTTP::Request::Common;
+
+BEGIN {
+ delete @ENV{qw( PATH IFS CDPATH ENV BASH_ENV )}; # Placates taint-unsafe Cwd.pm in 5.6.1
+ use_ok( 'WWW::Mechanize' );
+}
+
+my $agent = WWW::Mechanize->new;
+isa_ok( $agent, 'WWW::Mechanize', 'Created agent' );
+
+$agent->add_header( Referer => 'x' );
+my $req = GET( 'http://www.google.com/' );
+$req = $agent->_modify_request( $req );
+like( $req->as_string, qr/Referer/, q{Referer's in there} );
+
+$agent->add_header( Referer => undef );
+$req = $agent->_modify_request( $req );
+unlike( $req->as_string, qr/Referer/, q{Referer's not there} );