isMutable!(T) - intended/overlooked behaviour?

[Liam McSherry via Digitalmars-d]

Are the results produced by the following program intended 
behaviour for isMutable!(T)?

---
void main()
{
     import std.stdio  : writeln;
     import std.traits : isMutable;

     struct S
     {
         enum size_t constant_0        = 0;
         enum const(size_t) constant_1 = 0;
     }

     __traits(compiles, { S s; s.constant_0 = 1; }).writeln; // 
false

     isMutable!(typeof(S.constant_0)).writeln; // true
     isMutable!(typeof(S.constant_1)).writeln; // false
}
---

I know the documentation for isMutable!(T) says "Returns true if 
T is not const or immutable," but it would make sense to me if it 
returned false when given an enum. Is this maybe something to be 
corrected?