Does not work on FF 61.0 -- this is a real bummer for me!

I get also the error with "Unknown @ rule: @-moz-document"

This is the line: @-moz-document domain("wordpress.org") {
...
}

The style is local / custom style.
I am on macOS 10.12.6 Sierra

Is this connect to the release notes where it says Web Extensions are now running in its own process on macOS?

The strange thing is: the very same style loaded from userstyles.org runs perfectly fine still on FF 61.0 - strange.