proxy_buffer_size values are honored even if proxy_buffering is off

[Rv Rv]

At the http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_buffer_size, the documentation implies that 
the configuration proxy_buffer_size , proxy_buffers and proxy_busy_buffers will be honored only when proxy_buffering is turned on.

I had been seeing truncated responses of files which went away when I increased proxy_buffer_size even though proxy_buffering was turned off. I am running nginx1.5.8. Is this expected behavior ?

Thanks for any answers.
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