Error: Type <my_type> was defined more than once

I’m trying to update graphql from 0.9.6 to 0.10.1.
Does “Modularizing the schema” still working? Everything OK with v.0.9.6 and server won’t start with graphql@0.10.1.

I ran into the same issue when upgrading but for me, I had been accidentally including the type definition twice. I’d suggest a console.log of the finished schema to see if you are doing the same thing.