diff --git a/test/unit/custom_workflow_mailer_test.rb b/test/unit/custom_workflow_mailer_test.rb
index eeb9513..6dfc70f 100644
--- a/test/unit/custom_workflow_mailer_test.rb
+++ b/test/unit/custom_workflow_mailer_test.rb
@@ -48,7 +48,7 @@ def test_truth
 
   def test_custom_email_template
     CustomWorkflowMailer.deliver_custom_email @user2, subject: 'Subject', template_name: 'mailer/my_email',
-                                              template_params: { url: Rails.root }
+                                              template_params: { url: Rails.root.to_s }
     email = last_email
     assert text_part(email).body.include?('Body'), Rails.root.to_s
     assert html_part(email).body.include?('Body'), Rails.root.to_s