CSS variable in clamp() without default value

[kamenf]

When using CSS variable without default value in clamp() reports "The types are incompatible" error.

Example:

.my-class {
  font-size: clamp(0.5rem, var(--outer-size) / 7.5, 2rem);
}

generates:

Value Error : font-size The types are incompatible )

[ylafon]

Fixed, along with the use of unresolvable (at declaration time) variables in other mathematical functions.