Template specification conflict

[simendsjo]

The following program gives me
"Error: template t.S.__ctor(C) if(isSomeChar!(C)) conflicts with 
constructor t.S.this at t.d(4)"

Is this because char etc can be converted to uint? Shouldn't the 
template specification make this unambiguous?

import std.traits;

struct S {
     this(uint i) {}
     this(C)(C c) if(isSomeChar!C) {}
}

void main() {}