Rails throws 'load_missing_constant: expected path_to_x to define X', yet it does

My error:

/Users/-/.rvm/gems/ruby-2.3.1/gems/activesupport-5.0.0.1/lib/active_support/dependencies.rb:512:in `load_missing_constant': 
Unable to autoload constant Types::QueryType, expected /Users/-/project/app/graph/types/query_type.rb to define it (LoadError)

app/graph/schema.rb:

module Graph
  Schema = GraphQL::Schema.define do
    query Types::QueryType
  end
end

app/graph/types/query_type.rb:

module Graph
  module Types
    QueryType = GraphQL::ObjectType.define do
      name 'Query'
    end
  end
end

config/application.rb:

config.autoload_paths << "#{Rails.root}/app/graph"
config.autoload_paths << "#{Rails.root}/app/graph/interfaces"
config.autoload_paths << "#{Rails.root}/app/graph/types"
config.autoload_paths << "#{Rails.root}/app/graph/unions"

Rails correctly expects Types::QueryType to be defined in app/graph/types/query_type.rb, however - weirdly enough - somehow concludes that file does not define Types::QueryType, which it clearly does.

Even weirder: when jumping into a console, it only throws this error the first time Types::QueryType is requested. The second time however Types::QueryType resolves to the correct definition.

I'm probably doing something wrong here, but I just can't seem to find it.