diff --git a/test/geometry_test.rb b/test/geometry_test.rb
index abf7a5f..96ebd2a 100644
--- a/test/geometry_test.rb
+++ b/test/geometry_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'test_helper'
 
 class GeometryTest < Test::Unit::TestCase
@@ -77,7 +79,7 @@ class GeometryTest < Test::Unit::TestCase
     should "make sure the modifier gets passed during transformation_to" do
       assert @src = Paperclip::Geometry.parse("123x456")
       assert @dst = Paperclip::Geometry.parse("123x456>")
-      assert_equal "123x456>", @src.transformation_to(@dst).to_s
+      assert_equal ["123x456>", nil], @src.transformation_to(@dst)
     end
 
     should "generate correct ImageMagick formatting string for W-formatted string" do