undefined method `[]' for nil:NilClass

[dblock]

/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-swagger-0.10.0/lib/grape-swagger.rb:342:in `block (2 levels) in parse_entity_models'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-swagger-0.10.0/lib/grape-swagger.rb:333:in `each'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-swagger-0.10.0/lib/grape-swagger.rb:333:in `block in parse_entity_models'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-swagger-0.10.0/lib/grape-swagger.rb:323:in `each'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-swagger-0.10.0/lib/grape-swagger.rb:323:in `parse_entity_models'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-swagger-0.10.0/lib/grape-swagger.rb:620:in `block in setup'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-0.11.0/lib/grape/endpoint.rb:47:in `call'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-0.11.0/lib/grape/endpoint.rb:47:in `block in generate_api_method'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-0.11.0/lib/grape/endpoint.rb:247:in `call'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-0.11.0/lib/grape/endpoint.rb:247:in `run'
/Users/dblock/.rvm/gems/ruby-2.0.0-p598/gems/grape-0.11.0/lib/grape/endpoint.rb:195:in `block in call!'

I have nested :dimensions do ... in a presenter that is documented as an entity.