unable to install async_graphics with opam

"Jean Saint-Remy [email protected] [ocaml_beginners]" <[email protected]> Sat, 7 Jun 2014 00:03:59 -0700 (PDT)

Newsgroups	gmane.comp.lang.ocaml.beginners
Message-ID	<[email protected]>

Hi,

I am not sure why 'opam install async_graphics' fails. The error message says

/usr/bin/ocamlfind ocamldep -package async -package graphics -modules async_graphics.mli > async_graphics.mli.depends
+ /usr/bin/ocamlfind ocamldep -package async -package graphics -modules async_graphics.mli > async_graphics.mli.depends
ocamlfind: Package `async' not found
Command exited with code 2.


but 


opam install async returns

[NOTE] Package async is already installed (current version is 108.08.00).


Is there a --force option or some other unmet dependency that I should be trying? The ocaml version I am using is 3.12.1 (which opam allows you to have many different ones). Maybe ocamlfind needs to be told where to find the async library?


Thanks in advance,

jean