Can I just say thank you for the good error message. I'm sure I have used compilers (not Haskell) which would tell you that you have a problem but leave you to find where the two defintions are. Dominic. Encode.hs:8: Ambiguous occurrence `Octet' It could refer to either `Encode.Octet', defined at Encode.hs:7 or `ASNBaseTypes.Octet', imported from ASNBaseTypes at E ncode.hs:5 (at ./ASNBaseTypes.hi:34) make: *** [Encode.o] Error 1 ------------------------------------------------------------------------------------------------- To receive our special fares directly by email, register at http://www.britishairways.com/registration