OCaml version 4.03.0 is now officially supported. There are four different switches:

  • 4.03.0+mingw32
  • 4.03.0+mingw64
  • 4.03.0+flambda+mingw32
  • 4.03.0+flambda+mingw64

You can also install the pre-compiled binaries by adding a suffix-c to the switch, e.g opam switch 4.03.0+mingw64c. Bootstrapping is much faster this way, but the binaries might not work any longer, if the maintainers of the cygwin repository update their mingw64-gcc packages.