onSubmitRequest not received by add-ins?

[Radu]

Inside an add-in I subscribe to various events, OnSubmit included:
(InfoPath.XDocument)x.OnSubmitRequest +=
new
InfoPath._XDocumentEventSink2_OnSubmitRequestEventHandler(onSubmit);
void onSubmit(InfoPath.DocReturnEvent e);

All the other events (OnSign, OnLoad, etc) are trapped excepting for
OnSubmitRequest .
Please note OnSubmitRequest is working as expected when used from a form
template.

Any help would be appreciated
Thanks
Radu