rfs() doens't work inside calc()

[aerni]

I'm using RFS v9.0.3 with PostCSS. The rfs() function doesn't work when wrapped in a calc() function.

Input:

margin-right: calc(rfs(2rem) * 2);

Output:

margin-right: rfs(2rem) * 2;

Expected Output:

margin-right: calc(calc(1.325rem + 0.9vw) * 2);