Class sheet binding are not displayed if the document's content is in syntax 1.0 and perform an Include

I have a page with syntax 1.0 and the content is

#includeForm("an old sheet")

On this document I have an object of the class CLASS.

In the CLASS page, I have a class sheet binding.

When I remove the page content or I convert it to syntax 2.1, the sheet is displayed normally.