Adding local patch results in Makepkg error

[DemonicSavage]

When I add a local patch, Makepkg fails with

==> ERROR: Unknown download protocol: file
    Aborting...
Press enter to exit

[DemonicSavage]

It seems that file:// is unsupported: https://bbs.archlinux.org/viewtopic.php?id=266778

That said, running a Python HTTP server on the directory and adding http://127.0.0.1/path/to/local.patch as a remote patch works fine as a workaround.