pg_upgrade error regarding hstore operator

I am attempting to upgrade my organization's database cluster from 9.1.19 to 9.5.1 using the pg_upgrade utility. After some processing, the tool bails out with the following error in the log:

pg_restore: creating OPERATOR "public.=>"
pg_restore: [archiver (db)] Error while PROCESSING TOC:
pg_restore: [archiver (db)] Error from TOC entry 5660; 2617 5655672 OPERATOR => postgres
pg_restore: [archiver (db)] could not execute query: ERROR: syntax error at or near "=>"
LINE 1: CREATE OPERATOR => (
^
Command was: CREATE OPERATOR => (
PROCEDURE = "hstore",
LEFTARG = "text",
RIGHTARG = "text"
);

-- For binary upgrade, handle...

I tried dropping the operator before doing the upgrade but it's dependent on the existence of the hstore extension. Ideas?

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