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 ('6824d2f8e907731db03d1d86db81e353', -1, 1544865786, 1544865786, '0350da35', 7, 0, 0)

Line : 187
File : sessions.php