2 files changed, 5 insertions, 1 deletions
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 6f7e6f3128..0e8badc498 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -1765,7 +1765,7 @@ module ActionDispatch
               # and return nil in case it isn't. Otherwise, we pass the invalid name
               # forward so the underlying router engine treats it and raises an exception.
               if as.nil?
-                candidate unless @set.routes.find { |r| r.name == candidate } || candidate !~ /\A[_a-z]/i
+                candidate unless @set.named_routes.key?(candidate) || candidate !~ /\A[_a-z]/i
               else
                 candidate
               end
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 96e23c2464..518d4ca09c 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -140,6 +140,10 @@ module ActionDispatch
           routes[name.to_sym]
         end
 
+        def key?(name)
+          routes.key? name.to_sym
+        end
+
         alias []=   add
         alias []    get
         alias clear clear!