nginx + unicorn Entity is to large

Question

On my test server I have nginx + unicorn set up. And nginx client_max_body_size is set to 20M. But she user uploads file more then 1mb it return error 413 Entity is too large. nginx.

So, I don't quite understand what make this problem?

Is there any possibly to unicorn limit upload?

EDIT

I'am getting 500 error when user send POST method request (specifically large).