I was finally successful in getting text-icu to work on Windows 64 bits. This is probably an indication of what to expect in general for packages requiring FFI on Windows 64 bits. In the past, on 32 bits, the standard Windows binary distribution from the ICU site could be used together with msys/mingw, even though it was officially only for MSVC. This no longer seems to be the case for 64 bits. When I build text-icu in that way with a 64 bit GHC and the Windows 64-bit binary ICU distribution for MSVC, the resulting EXEs segfault as soon as any function from text-icu is called. There is no official ICU download for mingw-w64 binaries. But happily, the MSYS2 project does provide a pre-built ICU binary distribution for mingw-w64. It tends to be quite up-to-date; the current version is ICU 55.1. Note, however, that I was *not* able to use the partial MSYS2 that comes with MinGHC, because pacman seems to be missing. So the solution is: 1. Download and install 64-bit MSYS2, following the instructions on the site: http://msys2.github.io 2. In the MSYS2 shell window, get the ICU package for mingw-w64: pacman -S mingw64/mingw-w64-x86_64-icu 3. Now you can build the Haskell text-icu library using this command: cabal install --extra-lib-dirs="c:\path\to\msys64\mingw64\lib" --extra-include-dirs="c:\path\to\msys64\mingw64\include" text-icu 4. Provide the following DLLs with your EXE that uses text-icu: libicudt55.dll libicuin55.dll libicuuc55.dll libgcc_s_seh-1.dll libstdc++-6.dll Get them from: c:\path\to\msys64\mingw64\bin This not only compiles, but EXEs produced using this library actually run without segfaulting. You can even compile native Windows EXEs from C using ICU this way, with the gcc that is put on your path by the Haskell Platform installer (and probably also MinGHC, but I didn't try that). Just include -L and -I options to gcc with the same paths as above, and make sure to specify -licuuc -licudt etc. as needed. -Yitz