Template error and parallel foreach bug?

[simendsjo]

On 04.06.2011 20:04, Timon Gehr wrote:
> ulong SumMultiple3Or5_parallel(uint below) {
>      ulong sum;
>      foreach(i; parallel(iota(below))) {
>          if(i % 3 == 0 || i % 5 == 0)
>              sum += i; // low level data race here.
>      }
>      return sum;
> }
>
> Loop iterations in a parallel foreach loop must be independent of each other.
>

I thought paralellism was using locks behind the scenes. Guess I'll have 
to read the documentation then :)