RelayState not being set when Symfony firewall intercepts and redirects to IDP

[andrewmatthews]

When the Symfony firewall intercepts a request and redirects the user to the IDP for authentication, the RelayState is not included in the redirect to the IDP. Consequently, when the user is returned from the IDP, they end up on the home page of the Symfony application, rather than the page they were attempting to access.

Is this supported? If so, is this a configuration option that I have not included?