segfault on trivial usage of MutexARC<int>

Following program segfaults using rust 0.5 on Fedora 17:

extern mod std;

use core::task::_;
use std::_;

fn main() {
  let value = 0;
  let marc = arc::MutexARC(value);

  for int::range(0, 5) |_| {
    do spawn {
      do marc.access |v| { *v += 1; }
    }
  }
}
