What's the minimum privilege needed to alter a foreign key constraint?

What's the minimum privilege needed to alter a foreign key constraint?

My migration script stopped working after MySQL 5.5.41 fixed this bug:

• InnoDB permitted a foreign key to be created which referenced a parent table for which the user did not have sufficient privileges. (Bug #18790730)

I get this error:

SQLSTATE[42000]: Syntax error or access violation: 1142 REFERENCES command denied to user 'foo'@'localhost' for table 'core.users' (SQL: alter table user_baz add constraint user_baz_user_id_foreign foreign key (user_id) references core.users (id) on delete cascade on update cascade)

Which means I need to fix the privileges. What's the minimum privilege I need?