EXCLUDE, Gist and integers

Hi. I'm looking into adding daterange exclusions to some of my tables.
Following the documentation, I can do this no problem to prevent any
records from overlapping:

CREATE TEMP TABLE foo (
client_id integer,
start_date date NOT NULL,
end_date date,
EXCLUDE using gist (daterange(start_date,end_date) with &&)
);

But what I really want is no overlapping records on a per-client basis. I
optimistically tried this:

CREATE TEMP TABLE foo (
client_id integer,
start_date date NOT NULL,
end_date date,
EXCLUDE using gist (daterange(start_date,end_date) with &&,client_id with
=)
);

But Postgres responds thusly:

ERROR: data type integer has no default operator class for access method
"gist"
HINT: You must specify an operator class for the index or define a default
operator class for the data type.

Can someone tell me what's the easiest way to make this work? Thanks in
advance!

Ken

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