[MapProxy] mapproxy.config - WARNING - unknown 'client_timeout' in globals.http

[Stefan Schantz]

Hi,
I have some problems with my source-server and therefore I want to 
increase the client_time to 90 sec.
I tried to change the config-file, but it doesn't work.
mapproxy.config - File:

globals:
  http:
      client_timeout: 90

What is my mistake?

Thanks,
Stefan