iis 10 – IIS – Request filtering – failed request tracing not showing blocked file exentension

I have enabled the Failed Request Tracing in IIS 10. If I’m disabling the allow unlisted file name extensions within the request filtering, then the failed request logs are generated. I can only see the 404 status, but there is no information about the blocked extension.

ModuleName: RequestFilteringModule 
Notification: BEGIN_REQUEST
HttpStatus: 404 
HttpReason: Not Found 
HttpSubStatus: 7 
ErrorCode: (0x0) 

How can I get information which file extension has been blocked (to allow this extension)?