Issue with create site / ID1061

I have a create site step that works fine when the workflow is run manually. If I try to run it automatically when an item is created, I get "Failed to create site. ID1061: HttpContext.Current is null. This code path is only valid when in the execution context of ASP.NET."

I have the spadmin account in the "override credentials" section of the create site action.  I also have tried placing the create site action in a "run if" block with the "run as owner" option checked. But that doesn't help either.

I have created the item while logged in with spadmin, but still receive the same error. 

Any ideas? Thanks