[Haskell-cafe] no time profiling on my MacBookPro8,1

For this vanilla program

module Main where

main = print $ fib 40

fib 0 = 1 fib 1 = 1 fib n = fib (n - 1) + fib (n - 2)

with these commands $ ghc -prof -auto-all -rtsopts -O --make Main.hs -o Main $ ./Main +RTS -p all of the %time cells in the generated Main.prof file are 0.0, as is the total time count (0.00 secs and 0 ticks). The %alloc cells seem normal. Andy Gill noticed that if you compile with -threaded, the %time cells seem normal. I scanned the GHC Trac tickets specific to Mac OS X, but saw no titles that looked similar. Is this a known issue? Thanks.