diff --git a/actionpack/lib/action_dispatch/testing/integration.rb b/actionpack/lib/action_dispatch/testing/integration.rb
index 45439a3bb1..10d85037ae 100644
--- a/actionpack/lib/action_dispatch/testing/integration.rb
+++ b/actionpack/lib/action_dispatch/testing/integration.rb
@@ -335,7 +335,7 @@ module ActionDispatch
         klass = APP_SESSIONS[app] ||= Class.new(Integration::Session) {
           # If the app is a Rails app, make url_helpers available on the session.
           # This makes app.url_for and app.foo_path available in the console.
-          if app.respond_to?(:routes)
+          if app.respond_to?(:routes) && app.routes.is_a?(ActionDispatch::Routing::RouteSet)
             include app.routes.url_helpers
             include app.routes.mounted_helpers
           end
diff --git a/actionpack/test/dispatch/routing/non_dispatch_routed_app_test.rb b/actionpack/test/dispatch/routing/non_dispatch_routed_app_test.rb
new file mode 100644
index 0000000000..676a8c38d4
--- /dev/null
+++ b/actionpack/test/dispatch/routing/non_dispatch_routed_app_test.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+module ActionDispatch
+  module Routing
+    class NonDispatchRoutedAppTest < ActionDispatch::IntegrationTest
+      # For example, Grape::API
+      class SimpleApp
+        def self.call(env)
+          [ 200, { "Content-Type" => "text/plain" }, [] ]
+        end
+
+        def self.routes
+          []
+        end
+      end
+
+      setup { @app = SimpleApp }
+
+      test "does not except" do
+        get "/foo"
+        assert_response :success
+      end
+    end
+  end
+end