diff --git a/app/models/site/deployment.rb b/app/models/site/deployment.rb
index b3b8898..abd8249 100644
--- a/app/models/site/deployment.rb
+++ b/app/models/site/deployment.rb
@@ -44,8 +44,8 @@ class Site
       # @param :slash [Boolean]
       # @return [String]
       def canonical_url(slash: true)
-        canonical_deploy.url.tap do |url|
-          "#{url}/" if slash
+        canonical_deploy.url.dup.tap do |url|
+          url << '/' if slash
         end
       end
       alias_method :url, :canonical_url