Data structure to big to be marshalled

Hi
I am trying to marshal and write a data structure with Marshal.output_value.
Unfortunately, I get this error: "Fatal error: exception
Failure("output_value: object too big")".
This seems to mean that my OCaml data structure is too big to be marshaled
in the first place because it exceeds the max size to be stored in header:
http://caml.inria.fr/svn/ocaml/branches/record-disambiguation/byterun/extern.c
.

Is there any canonical way to bypass this size limitation ?
Or do I just have have to "manually" split my data structure, marshal the
splits, unmarshal the splits and merge them ?

Johan