4.5 ModelBinding server side validation (dataanotations) does not work properly with custom usercontrol on page

FormView validates properly at server side my custom annotations, but if a custom usercontrol is added (before or after formview) validation is not reflected on client side, 'Page_Validators' variable does not contain proper validation data ('isvalid' property is always undefined in all validators), and besides, InsertMethod is never reached.
Actually, my custom usercontrol draws a plain HTML table.