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 ('05d7ccd40ce17c3039eca11451e49a12', -1, 1488300581, 1488300581, '36cd6a8a', -1, 0, 0)

Line : 187
File : sessions.php