How do I express x is not null in honeysql?

[:raw "username is not null"]

[:not= nil :username]

dev=> (sql/format {:where [:is-not nil :x]})
["WHERE x IS NOT NULL"]
dev=> (sql/format {:where [:<> nil :x]})
["WHERE x IS NOT NULL"]
dev=> (sql/format {:where [:not= nil :x]})
["WHERE x IS NOT NULL"]

the possibilities are endless!