phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('9e600483ffc4784914a4cd91cfa3644e', -1, 1422217078, 1422217078, '36edf7ac', -1, 0, 0)

Line : 189
File : sessions.php