The unit of the variable for @for is inconsistent between implementations

With this input

test {
    @for $i from 12px to 13px {
        content: unit($i);
    }
}

I get the following output on ruby-sass 3.7.4 and libsass 3.5.5 (these are the versions available on https://www.sassmeister.com/):

test {
  content: "px";
}

But I get this output on dart-sass 1.26.10 and 1.26.11

test {
  content: "";
}

IMO, the behavior of ruby-sass and libsass is more logical, as the values for from and to are handled as unit numbers (including coercing compatible units).

[babakfp]

Just curious, why you used px (for loop parameters)?

[nex3]

Thanks for all your help with this, @stof!