diff --git a/lib/roby/actions/models/interface.rb b/lib/roby/actions/models/interface.rb
index 7c7b7d03e..cf8ee2496 100644
--- a/lib/roby/actions/models/interface.rb
+++ b/lib/roby/actions/models/interface.rb
@@ -91,6 +91,7 @@ def register_action(name, action_model)
                         end
                         const_set task_model_name, task_model
                         task_model.permanent_model = self.permanent_model?
+                        action_model.returns(task_model)
                     end
                 end