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 ('ee8787791e0b33ef3c5ee963ad703ab2', -1, 1540278988, 1540278988, '365ca077', 12, 0, 0)

Line : 187
File : sessions.php