[Haskell-cafe] approxRatio and Ratio Word

I have been experiencing curious behaviour with approxRatio: Prelude Data.Ratio> let a = 0 :: Word Prelude Data.Ratio> let b = 10 :: Word Prelude Data.Ratio> a%b 0 % 1 Prelude Data.Ratio> approxRational (a%b) 0.01 1 % 1 Prelude Data.Ratio> approxRational (0%1) 0.01 0 % 1 Is this expected? If so, why?