linker errors

Hello There, this is my first post on this list. I'm quite new to using Haskell (started in July), so my question might be somewhat trivial, but I still hope you can help me out. At the moment our project - a parser for a type language - consists of the following modules: Lexer IntermediateSyntax Parser (from a Happy source file) - uses Lexer and IntermediateSyntax Main - uses Parser When compiling using ghc, I get the following error: Parser.o(.text+0x10fc5): In function `r1fgN_entry': : undefined reference to `DataziTuple_Z77T_con_info' collect2: ld returned 1 exit status I neither know the function `r1fgN_entry' nor `DataziTuple_Z77T_con_info'. So what is it? Thanks in advance, Frank-Andre Riess