phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('6716e04cca7d4b7261d474f61b2c82ab', -1, 1540330031, 1540330031, '36e05922', 8, 0, 0)

Line : 187
File : sessions.php