Filter list not working with frappe.db.exists

I try to use frappe.db.exists with a filter list instead of dict (because I want to check if a field is empty). However it is not working.


frappe.db.exists("Time Tracking", [["employee", "=", "HR-EMP-00001"]])

Same example with dict filter returns true:

frappe.db.exists("Time Tracking", {"employee": "HR-EMP-00001"})

The employee field of the Time Tracking DocType is a Link to the ERPNext Employee DocType.