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 ('e9ba65a17bc576c1429a668e13a65e36', -1, 1540286638, 1540286638, '36a174e1', -4, 0, 0)

Line : 187
File : sessions.php