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 ('38d8344a1ed788f83557b8c94c58d4cb', -1, 1540275960, 1540275960, '365057a6', 6, 0, 0)

Line : 187
File : sessions.php