backtrace doesn't show symbol names on Windows

[klutzy]

fn main() { fail!("abc"); }

task '<main>' failed at 'abc', a.rs:3
stack backtrace:
   1:   0x4987bd
   2:   0x4b1f2c
   3:   0x401779
   4:   0x401677
   5:   0x42b910
   6:   0x4b1855
   7:   0x4af9e6
   8:   0x42b7df
   9:   0x42b691
  10:   0x4016c0
  11:   0x4013e2
  12: 0x7547919f
  13: 0x77a6a22b

Both win32 and win64.
(Afaik this is long-standing issue but just not received a ticket before?)