Local file names containing spaces exposed with + on S3

[bmedici]

When I put a file named "source/The File.pdf" in my local source directory, it is built by middleman and then pushed to s3 but any link pointing to it breaks.
In fact, the file is seen as "source/The+File.pdf" inside the S3 bucket, and only working with a link like href="source/The+File.pdf".

How should I configure s3_sync to force S3 to used spaces instead of pluses, but I guess s3 is working this way and it's not possible ?
How should I tell middleman to anticipate a link to a name with pluses like S3 will transform it ?

Thanks for your tips.