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 ('0ef5ce904b1ea9c4f1be2ba7164b6c30', -1, 1467301243, 1467301243, '3650dcb0', -1, 0, 0)

Line : 187
File : sessions.php