HTTP 403 Forbidden on accessing layouts pages from a SharePoint 2013 app web

I have added the report content types (that comes with reporting services) to a document library in an app web.

But when creating an new report by the ribbon > New document I get a 403 Forbidden (also if you want to open a report that you have uploaded to the library)

For creating a new file by the "New document" drop down it wants to access the following page: _layouts/15/ReportServer/RSAction.aspx (and adds some parameters)

But for creating data sets, data sources, reports or viewing them it always needs aspx pages in the _layouts/15/ReportServer/ folder. But you always get a 403 Forbidden.

In a library in the host web, it works perfect.

Anybody any ideas?