diff --git a/test/test_heuristics.rb b/test/test_heuristics.rb
index 4a156445..a13ae12a 100644
--- a/test/test_heuristics.rb
+++ b/test/test_heuristics.rb
@@ -48,8 +48,7 @@ class TestHeuristcs < Minitest::Test
   def test_pl_prolog_perl_by_heuristics
     assert_heuristics({
       "Prolog" => all_fixtures("Prolog/*.pl"),
-      "Perl" => all_fixtures("Perl/*.pl"),
-      "Perl" => ["Perl/perl-test.t"],
+      "Perl" => all_fixtures("Perl/*.pl") + ["Perl/perl-test.t"],
       "Perl6" => all_fixtures("Perl6/*.pl")
     })
   end