How to filter messages that do NOT have attachments using GMail query language?

Question

How do I filter out Gmail messages that DO NOT have attachments?

Here is the documentation I'm trying to follow.

I can see that in order to include messages with attachments, I use the following query:

has:attachment

However, I do not see a way to do the inverse. I seek something like:

!has:attachment

What am I missing?

Answer 1

Summary from comments

Both of the following work:

!has:attachment

and

-has:attachment