Not In clause not working as expected

[vsalbaba]

Given posts with ids [1,2,3]
When I do
Post.where(:id.not_in => [])
I expect result to be [1,2,3].

The current generated query is
SELECT posts.* FROM posts WHERE posts.id NOT IN (NULL)

Which returns [].
So, Post where id is not in empty array returns instead of all posts .. an empty array.