ERROR: Index pg_toast_8443892_index is not a btree

I get the following error when vacuuming a db or inserting
a big value in a column of a toastable datatype (GEOMETRY).

ERROR: Index pg_toast_8443892_index is not a btree

My last action has been killing a psql that was getting
mad about receiving too much input and beeping as hell
(readline issue ?).

After that, I put the insert query I was trying to feed to
psql in a file and sourced it... Bump! that error appeared.

psql:B:477: ERROR: Index pg_toast_8443892_index is not a btree

Line 477 is EOF...

Vacuum does not solve this (as you can see in the first error message)

Do you have any hint about how to fix this ?

TIA

--strk;