RDoc duplicate entries

This has happened to me before, and (sigh) I can’t recall what it was
–or if I ever actually figured out.

When I run RDOC:

rdoc --op=‘doc/rdoc’ --inline-source --template=‘jamis’ –
main=‘README’ CHANGES README Metadata NEWS COPYING lib/anno.rb lib/
anno/attributes.rb lib/anno/annotations.rb lib/anno/anno.rb

I get rdocs with every file and method appearing twice. Now, I know
this can happen if you repeat entries on the command line (which I
consider a bug btw), but I haven’t repeated any here, so I don’t
understand why I’m getting duplicate entries.