diff --git a/core/lib/spree/testing_support/extension_rake.rb b/core/lib/spree/testing_support/extension_rake.rb
index f03d87ce527..4597fa4465a 100644
--- a/core/lib/spree/testing_support/extension_rake.rb
+++ b/core/lib/spree/testing_support/extension_rake.rb
@@ -4,8 +4,8 @@
 
 desc "Generates a dummy app for testing an extension"
 namespace :extension do
-  task :test_app, [:user_class] do |_t, _args|
+  task :test_app, [:user_class] do |_t, args|
     Spree::DummyGeneratorHelper.inject_extension_requirements = true
-    Rake::Task['common:test_app'].invoke
+    Rake::Task['common:test_app'].invoke(args[:user_class])
   end
 end