In call to intarweb#read-request during spiffy#handle-incoming-request:

Incoming spiffy with bloaty header: exn

        Call history:

        string-null?      
        string-take-right         
        intarweb#safe-read-line   
        intarweb#http-line-limit          
        intarweb#http-line-limit          
        read-line         
        intarweb#signal-http-condition    
        make-property-condition   
        make-property-condition   
        make-composite-condition          
        signal    
        k642648   
        g646647   
        close-input-port          
        display   
        with-output-to-string           <--

and that's that!