diff --git a/actionpack/lib/action_dispatch/journey/router/utils.rb b/actionpack/lib/action_dispatch/journey/router/utils.rb
index ffcd875b4df73b9c55a81cbcc812d22f75c31262..f937597c1b10f1e8aba8d28e483af864e78f133c 100644
--- a/actionpack/lib/action_dispatch/journey/router/utils.rb
+++ b/actionpack/lib/action_dispatch/journey/router/utils.rb
@@ -84,6 +84,10 @@ def self.escape_fragment(fragment)
           ENCODER.escape_fragment(fragment.to_s)
         end
 
+        # Replaces any escaped sequences with their unescaped representations
+        #
+        #   uri = "/topics?title=Ruby%20on%20Rails"
+        #   unescape_uri(uri)  #=> "/topics?title=Ruby on Rails"
         def self.unescape_uri(uri)
           ENCODER.unescape_uri(uri)
         end