can't reproduce example

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.5/static/rangetypes.html
Description:

I tried to reproduce the example :
CREATE EXTENSION btree_gist;
CREATE TABLE room_reservation (
room text,
during tsrange,
EXCLUDE USING GIST (room WITH =, during WITH &&)
);

but I got this error :
ERROR: data type text 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.

That means by default nobody is able to reproduce your example... Howto use
gist with text or varchar?