diff --git a/actionpack/lib/action_dispatch/journey/formatter.rb b/actionpack/lib/action_dispatch/journey/formatter.rb
index 992c1a9efedf01110a7e6fe5ef5c09d5776aa640..62bd4a33f24016061cadac15361a61ae50ac83ed 100644
--- a/actionpack/lib/action_dispatch/journey/formatter.rb
+++ b/actionpack/lib/action_dispatch/journey/formatter.rb
@@ -1,4 +1,5 @@
 require 'action_controller/metal/exceptions'
+require 'active_support/deprecation'
 
 module ActionDispatch
   module Journey
@@ -80,6 +81,15 @@ def match_route(name, options)
           if named_routes.key?(name)
             yield named_routes[name]
           else
+            if name
+              ActiveSupport::Deprecation.warn <<-MSG.squish
+                You are trying to generate the URL for a named route called
+                #{name.inspect} but no such route was found. In the future,
+                this will result in an `ActionController::UrlGenerationError`
+                exception.
+              MSG
+            end
+
             routes = non_recursive(cache, options)
 
             hash = routes.group_by { |_, r| r.score(options) }