Cannot access WMS.GetMap as anonymous

version geoserver 2.6.2

I have a problem with the WMS service

to authenticate the service wms configure the following rule in " List of access to services"

wms.GetMap ROLE_AUTHENTICATED

but the response this url

http://localhost/geoserver/xxxx/wms?service=WMS&version=1.1.0&request=GetMap&layers=xxxx:clientes&styles=&bbox=.......&width=378&height=512&srs=EPSG:4326&format=application/openlayers

is

Estado HTTP 500 - Request processing failed; nested exception is org.springframework.security.authentication.InsufficientAuthenticationException: Cannot access WMS.GetMap as anonymous

thanks for your help