MobilePage and Inheritance

Hello, i have a class "X" which inherits MobileControls.MobilePage

in my ASPX page (with no codebehind), it Inherits "X"

but when i switch to designer mode, every mobile controls displays
"This control only works in pages of type MobilePage"

I still can access properties of the controls in designer mode, but
the controls in Mobile WebForms Toolbox is disabled, and is very
irritating.

There's one similar problem i found on the net, solved using
CodeFileBaseClass, but only for page with codebefind file.

Help greatly appreciated.