Ocaml for windows 10 compile error

Followed the instructions at https://fdopen.github.io/opam-repository-mingw/installation/
Using Windows 10 home version 1809 (recent).

Tried both the graphical installer and manual installation.

Got the same error when trying to compile:

$ ocamlfind ocamlopt -o rho_z -linkpkg -package zarith rho_z.ml
Cannot set stack reserve: File “coff.ml”, line 946, characters 4-10: Assertion failed

my stack limit (on Cygwin) is 65 MB
~/ocaml/rho_mp_timing$ ulimit -s

It’s caused by flexdll:

Try to compile it again with verbose settings:
export FLEXLINKFLAGS='-v -v -v' ; ocamlfind ocamlopt ...
Perhaps you can notice something unusual. It’s hard to guess without knowing the source.

Btw: Don’t use -o foo on windows, always use -o foo.exe.

I used the binaries from github, and they worked fine. Thank you!