ChangeNotifierProxyProvider is giving a possible null error

Question

So, following the ChangeNotifierProxyProvider docs I have implemented the following:

   ChangeNotifierProvider<AuthProvider>(
      lazy: false,
      create: (BuildContext createContext) => AuthProvider(),
    ),
    ChangeNotifierProxyProvider<AuthProvider, APIService>(
        create: (_) => APIService(),
        update: (_, auth, api) => api..update(auth),
    ),

This is how it is recommend to implement it in the docs, however i am getting and error:

 The return type 'APIService?' isn't a 'APIService', as required by the closure's 
 context.

Would it be correct to change api..update(auth) to api!..update(auth)? Why was this not need in the example provided in the docs.