Should pg 11 use a lot more memory building an spgist index?

While reloading a database cluster to move from 10.5 to 11, I'm getting
out of memory crashes that I did see when doing reloads on pg 10.
The statement flagged in the log is this:
2018-10-23 16:44:34.815 CDT [126839] STATEMENT: ALTER TABLE ONLY public.iplocation
ADD CONSTRAINT overlap EXCLUDE USING spgist (network WITH &&);

iplocation has 4398722 rows.

This is geolite data where the networks are a partial covering of the total
address spaces with no overlaps.

Should I expect to have to make config changes to make this work?