ocaml-ancient @0.9.0: incompatible pointer types initializing 'char *' with an expression of type 'header_t *'

[ryandesign (Ryan Carsten Schmidt)]

​https://build.macports.org/builders/ports-10.13_x86_64-builder/builds/36711/steps/install-port/logs/stdio

gcc -g -fPIC -Wall -Werror -DOCAML_VERSION_MAJOR=4 -DOCAML_VERSION_MINOR=7 -I/opt/local/lib/ocaml   -c -o ancient_c.o ancient_c.c
ancient_c.c:208:9: error: incompatible pointer types initializing 'char *' with an expression of type 'header_t *' (aka 'unsigned long *') [-Werror,-Wincompatible-pointer-types]
  char *header = Hp_val (obj);
        ^        ~~~~~~~~~~~~
1 error generated.
make: *** [ancient_c.o] Error 1

It's also not UsingTheRightCompiler.