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 ('c2f16d0f76406b79f382809963bde621', -1, 1467327285, 1467327285, '36e0e215', -1, 0, 0)

Line : 187
File : sessions.php