asp:ServiceReference to web service behind a reverse proxy with ASP.NET 4.0

Hi,
we are currently migrating our application from ASP.NET 3.5 to 4.0 and we ran into a problem accessing a AJAX-enabled WCF web service.
Both the client ASPX pages and the web service run in the same ASP.NET application. The server is never directly accessed: it is accessed via a reverse proxy that also provides SSL encryption.
So what we have is
ASPX page ----------> reverse proxy ------> Web service
             HTTPS                   HTTP
With .NET 3.5 SP1 this was not a problem, but on .NET 4 the web service proxy (generated using an asp:ServiceReference tag) incorrectly tries to use the HTTP protocol. So instead of making the request to https://myserver.mydomain/MyApp/Services/MyService.svc i ...