Parse error with CSS custom properties with default values including a nested calc

The following CSS:

div {
    margin-right: calc(var(--b, calc(var(--c) * 1)));
}

Leads to the following parser error:

JisonParserError: Parse error on line 1: 
var(--b, calc(var(--c)*1))
-------------------------^
Expecting end of input, "ADD", "SUB", "MUL", "DIV", got unexpected "RPAREN"

Looking at the Stack trace, here’s the chain of the last few operations leading to the issue:

at Parser.parseError (/node_modules/postcss-calc/dist/parser.js:1164:15)
at Parser.parse (/node_modules/postcss-calc/dist/parser.js:1680:30)
at /node_modules/postcss-calc/dist/lib/transform.js:30:30

Removing the last * 1 part removes the parser error.

[eric1iu]

As a workaround, disable postcss-calc in package.json to pass gatsby build in my case.

  "cssnano": {
    "preset": [
      "default",
      {
        "calc": false
      }
    ]
  }

Will enable again once this bug fixed. Thanks!

[HZooly]

Any example of this for removing postcss-calc from Gatsby build please? I can’t achieve this…

I tried to edit my postcss.config.js, unsuccessful.