Is it possible to apply a conditional to the map background in Mapbox Studio?

Question

I'm trying to do the following, but it seems like conditionals are completely bypassed within the Map block:

@invert: 'No';

Map 
{  
  [@invert = "No"] 
  { 
    background-color: green;
  } 
  [@invert = "Yes"] 
  { 
    background-color: red;
  }
}

When @invert is set to "No", background color is green, when @invert is set to "Yes", background color is green. It's as if it skips right over the conditional and simply uses the first instruction and ignores the second. This is normal behavior if no conditionals exist and the same instruction is set twice, but I've never experienced this issue when using conditionals except in the Map block.

Is there a mistake here I'm not seeing, or a possible work around?