Variable declaration in .less files being marked as errors of "Unexpected missing generic font family"

I’m getting a bunch of errors in .less files when declaring variables.

//Z-index //Getting an error here
@zIndex1: 1000;
@zIndex2: 2000;
@zIndex3: 3000; //Getting an error here
@zIndex4: 4000;
@zIndex5: 5000;
@zIndex6: 6000; //Getting an error here
@zIndex7: 7000;
@zIndex8: 8000;
@zIndex9: 9000; //Getting an error here

The error is always this one - Rules explorer

I think the analyzer believes I’m declaring a @fontFace since it starts with an @, and is wrongly marking the code as an error.
Although it doesn’t make much sense because it isn’t happening in every instance where I’m declaring a variable, just on some lines and it appears to be completly random.

Any help with this issue?