SharePoint 2013 - CQWP include child content types issue

Hello SharePoint enthousiastes,

I'm experimenting a weird issue with the content query webpart in SharePoint 2013.

In the query part of the webpart settings, in the Content type section, I want to untick the "Include child content types" option >

Content Type:
Show items of this content type group:
Show items of this content type:

	 
Include child content types
	

The checkbox stays ticked even if I click on apply or ok to validate the setting.

Is it a bug? What am I missing?

It always worked directly in the previous version of SharePoint (2007/2010) so I don't understand why is it not working directly with 2013.

Thanks in advance for your replies.

BR,