Hi, Here is a question about a non-standard build from a first-timer ... I am slowly making progress, in a drunken walk kind of way, building GHC 6.7.20070518 (the one from the LambdaVM tree). Whilst most of my problems can be side stepped by tweaking the configure options and my libraries, I am puzzled by the error below. Why is MutableByteArray being used? Isn't it deprecated? Its appearance does sit inside #ifdef mingw32_HOST_OS so maybe it hasn't been noticed. Mark ./configure --enable-java --build=i386-unknown-mingw32 --with-gcc=c:/software/mingw/bin/gcc --with-ld=c:/software/mingw/bin/ld.exe <snip> ../../compiler/ghc-inplace -H16m -O -fglasgow-exts -cpp -Iinclude -"#include" HsBase.h -funbox-strict-fields -package-name base-2.0 -O -Rghc-timing -fgenerics -fgenerics -c GHC/Conc.lhs -o GHC/Conc.o -ohi GHC/Conc.hi GHC/Conc.lhs:607:43: Not in scope: type constructor or class `MutableByteArray#' GHC/Conc.lhs:609:33: Not in scope: `byteArrayContents#' GHC/Conc.lhs:611:44: Not in scope: type constructor or class `MutableByteArray#'