"could not split GIN page; no new items fit"

create index foo_idx on foo using gin(entry gin_trgm_ops);

and I'm getting the error "could not split GIN page; no new items fit"

Any idea what this means, or how I can get around it?  The table in question has about 23MM rows, if that makes any difference.  The only reference that search engines returned was the source code.

select version()

PostgreSQL 9.4.1 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.9.1-16ubuntu6) 4.9.1, 64-bit

-Chris