StoreFront Update 3.5 to 3.6 failed

Trying to upgrade our Storefront Cluster, we ran into trouble. Unable to upgrade its, in the logs from c:\Windows\temp\Storefront we found the following error
citrix.deliveryservices/protocolTransitionSettings : Unable to load file or assembly(…)

To make the update work, the “C:\program files\Citrix\Receiver Storefront\Services\ProtocolTransitionService\Citrix.DeliveryServices.ProtocolTransition.ServiceHost.exe.config” files should be modified after the line 4, version “3.0.0.0” had to be replace with 3.5.0.0

source : https://discussions.citrix.com/topic/378442-stf-36-upgrade-from-stf-35-to-36/