Clogfileroute Has No Property "except"

This config

‘log’=>array(

		'class'=>'CLogRouter',


		'routes'=>array(


			array(


				'class'=>'CFileLogRoute',


				'levels'=>'info,error,warning',


                            'except' => 'system.web.*', 


			),


		


		), 


	),

produces this error:

Property \"CFileLogRoute.except\" is not defined.

Any insights?

Thanks.