Slim Upload MediaType

I am trying to load a file with a slim framework, I am trying to upload a file, to the server using postman, when I call a machine different from the server machine I can get the mediatype , but if I execute one Calls with the postman installed inside the server I always get the same mediatype “application/octet-stream”

function $file->getClientMediaType()

I am sending a .xlsx file but on the server I have no .xlsx reader, I have tested from inside the server with .pdf and it sends the correct mime type

Perhaps there is a setting in postman to set the mediatype?