Fulltext search doesn't work with NOT LIKE operator

I noticed the problem as I was using the Smart Search on a 5.4.2, but it also occurs on the Intranet (5.6 + HF).

Using the Smart Search, there is an operator NOT LIKE (available for all text fields). However when I try to use it, I get this error: "Failed to execute query: ecm:fulltext requires = or LIKE operator".