diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index c23577de9bc65d497ef68719bd3cd2b12d1ed37a..59460cbe82ebea36e5dc6c3eeff390a6aea8dd7a 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,3 +1,11 @@
+*   The method `shallow?` returns false if the parent resource is a singleton so
+    we need to check if we're not inside a nested scope before copying the :path
+    and :as options to their shallow equivalents.
+
+    Fixes #14388.
+
+    *Andrew White*
+
 *   Make logging of CSRF failures optional (but on by default) with the
     `log_warning_on_csrf_failure` configuration setting in
     `ActionController::RequestForgeryProtection`.
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index 357829e59f6028908b77fe84fd7646e1db22d3e2..5de0a0cbc65a3edc8a20e1ae39f8373f832b090d 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -707,7 +707,7 @@ def scope(*args)
           options[:path] = args.flatten.join('/') if args.any?
           options[:constraints] ||= {}
 
-          unless shallow?
+          unless nested_scope?
             options[:shallow_path] ||= options[:path] if options.key?(:path)
             options[:shallow_prefix] ||= options[:as] if options.key?(:as)
           end
@@ -1547,6 +1547,10 @@ def resource_method_scope? #:nodoc:
             RESOURCE_METHOD_SCOPES.include? @scope[:scope_level]
           end
 
+          def nested_scope? #:nodoc:
+            @scope[:scope_level] == :nested
+          end
+
           def with_exclusive_scope
             begin
               old_name_prefix, old_path = @scope[:as], @scope[:path]
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index a47050adceb408bbcc7d8d5aa69863a39f28cbf4..ab2f0ec8de3f3885e0a2551c966e69215bbeff3a 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -1958,6 +1958,42 @@ def test_shallow_nested_resources
     assert_equal '/comments/3/preview', preview_comment_path(:id => '3')
   end
 
+  def test_shallow_nested_resources_inside_resource
+    draw do
+      resource :membership, shallow: true do
+        resources :cards
+      end
+    end
+
+    get '/membership/cards'
+    assert_equal 'cards#index', @response.body
+    assert_equal '/membership/cards', membership_cards_path
+
+    get '/membership/cards/new'
+    assert_equal 'cards#new', @response.body
+    assert_equal '/membership/cards/new', new_membership_card_path
+
+    post '/membership/cards'
+    assert_equal 'cards#create', @response.body
+
+    get '/cards/1'
+    assert_equal 'cards#show', @response.body
+    assert_equal '/cards/1', card_path('1')
+
+    get '/cards/1/edit'
+    assert_equal 'cards#edit', @response.body
+    assert_equal '/cards/1/edit', edit_card_path('1')
+
+    put '/cards/1'
+    assert_equal 'cards#update', @response.body
+
+    patch '/cards/1'
+    assert_equal 'cards#update', @response.body
+
+    delete '/cards/1'
+    assert_equal 'cards#destroy', @response.body
+  end
+
   def test_shallow_nested_resources_within_scope
     draw do
       scope '/hello' do