This error append when trying to upload a file bigger than 1Mbits on a platform using Nginx as an HTTP server or reverse-proxy/SSL off-loader. That because Nginx, by default, limit client query size.
You can change the upper value using the client_max_body_size directive into Nginx setting file:
# vi /etc/nginx/nginx.conf
client_max_body_size <new_value>;
Note: if you want to disable this behavior, set the value to 0.