can't save with specific file permission

[pomponfrais]

Maybe i'm doing something wrong or there is something i misunderstand server side but I can not save a new file with some specific permission using "filePermissions": "0644" in the configuration file. It keeps saving file with "600" permission. I'm using sftp. I always have to connect to my server through ssh and change file permission manually. Any clue concerning this behavior ? thanks ! :)