Hi there

I really enjoy susy so far. I also specifically like the feature susy-svg-grid() to display the grid svg.
So far I always used it with a fluid configuration:

$susy: (
  'columns': susy-repeat(8), // makes 8 fluid columns
  'gutters': 0.13, // unitless gutter as fraction, on the same scale as any unitless columns
);

But now I want to use a fixed width:

$susy: (
  'columns': susy-repeat(8), // makes 8 fluid columns
  'gutters': 20px, 
);

The gutter is taken into account when displaying my layout, but unfortunately the grid svg in the background would just disappear.
I can see the base64 encoded svg but it would not show up:

If I change it back to the unitless gutter I can see it again...

If you compare the two screenshots, you can see a difference with the calc() part.
Is this maybe not working correctly? Did you ever experience something similar?
Or any idea where I could look for bugs?
It's really just the gutters I change and the grid disappears...

Cheers and thanks

Edit:
I just edited the svg code in the inspector, and I changed one of the values looking like
width="calc(((100% - 7.7778rem) / 8 * 1))"
to something like width="10%" which would immediately show me one of the grid bars.
So I assume this calc stuff must cause an error, although I don't know how to fix it.