Problem while fetching service bus metrics

Hi,

I am trying to get ServiceBus metrics using the following url

https://management.core.windows.net/{subc-id}/services/servicebus/Namespaces/{queue-namespace}/Queues/{queeu-name}/Metrics/size/Rollups/PT1H/Values?$filter=timestamp%20gt%20'2014-09-11T09:00:00Z'

But it is throwing 500 error. Is my filter wrong? or am I missing something.

Thanks for the help.

Regards,

Satish