How to filter on empty string value list items using Rest API

I'm trying to get the items from a list "MyList" where Title is empty. I'm using the following Url:

_api/web/lists/getbytitle('MyList')/items?$select=Title&$filter=Title eq ''

It returns me all items weither Title is empty or not.
I've also tried ne null, with same result. Also length(Title) eq 0 displays "The query is not valid"

Is there a way to do it with Rest Api?

Any help will be greatly appreciated

Olivier