[racket] identifier is already imported

Hi,

I uploaded a package to planet that was working fine in
my machine.  However, those who downloaded it report
that the installation produces the following message:

module: identifier is already imported
raco setup: error: during making for <planet>/aml/rosetta.plt/1/2/base
raco setup:   module: identifier is already imported

Unfortunately, the error message doesn't show which
identifier is already imported so I don't know what to do
to solve the problem.

BTW, in spite of the message, the package seems to run fine.

Any ideas?

Thanks,
Antonio.