Unassigned Users Not Being Returned When Searching for Issues Not Assigned to Specific User

I have a JQL search which is supposed to return all issues which I am watching but not the assignee or reporter. The original search I wrote is:

status != closed and watcher = "myusername" and reporter != "myusername" and assignee != "myusername"

However, it appears that the parameter "assignee != "myusername" " does not return issues that are completely unassigned, which means I had to alter the search to be:

resolution = EMPTY and watcher = "myusername" and reporter != "myusername" and (assignee != "myusername" or assignee is empty).

This seems like bad logic to me; if an issue is unassigned, its by definition not assigned to me. Can this be fixed?