--- /dev/null
+#!perl -T
+
+use strict;
+use warnings;
+
+BEGIN { $ENV{PERL_FORCE_TEST_THREADS} = 1 }
+
+use VPIT::TestHelpers threads => [ 'Not::Thread::Safe', 0 ];
+
+use Test::More tests => 1;
+
+fail 'force should not overrule thread-unsafe';
+
+my $thread = spawn sub { };
+$thread->join;