TypeScript: Can't find name error when accessing interface across multiple files

I am trying to create some definition files for a personal project. (I am recreating the context here with different class / module names, so the modeling might not make much sense).

I have the following interface definition file that has no dependencies and compiles fine:

// File: automobile.d.ts
declare module Transport {
    interface Automobile {
        // ... variables and functions
        accelerate(direction:String):Boolean;
    }
}

      

        
        
        
      

    

However, in this file, when I try to reference Automobile

in this file in the same module Transport

, I get Cannot find name 'Automobile'

.

// File: automobile_collection.d.ts
declare module Transport {
    interface AutomobileCollection {
        size:Number;
        getItemAt(index:Number): Automobile;
    }
}

      

        
        
        
      

    

I tried to export the interface, but it didn't help. Any ideas what I am doing wrong?