diff -urN ocaml-3.12.0.orig/otherlibs/unix/unixsupport.h ocaml-3.12.0/otherlibs/unix/unixsupport.h
--- ocaml-3.12.0.orig/otherlibs/unix/unixsupport.h	2011-04-06 18:44:37.000000000 -0500
+++ ocaml-3.12.0/otherlibs/unix/unixsupport.h	2011-04-06 18:56:48.000000000 -0500
@@ -23,6 +23,8 @@
 extern void unix_error (int errcode, char * cmdname, value arg) Noreturn;
 extern void uerror (char * cmdname, value arg) Noreturn;
 
+#define Fd_of_val(handle) Int_val(handle)
+
 #define UNIX_BUFFER_SIZE 16384
 
 #define DIR_Val(v) *((DIR **) &Field(v, 0))
diff -urN ocaml-3.12.0.orig/otherlibs/win32unix/unixsupport.h ocaml-3.12.0/otherlibs/win32unix/unixsupport.h
--- ocaml-3.12.0.orig/otherlibs/win32unix/unixsupport.h	2011-04-06 18:44:37.000000000 -0500
+++ ocaml-3.12.0/otherlibs/win32unix/unixsupport.h	2011-04-06 18:55:13.000000000 -0500
@@ -42,6 +42,7 @@
 extern value win_alloc_handle(HANDLE);
 extern value win_alloc_socket(SOCKET);
 extern int win_CRT_fd_of_filedescr(value handle);
+#define Fd_of_val(handle) win_CRT_fd_of_filedescr(handle)
 
 #define NO_CRT_FD (-1)
 #define Nothing ((value) 0)