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 ('c1c05dcb90d0a2266d76dbaf2a21de47', -1, 1540147349, 1540147349, '3691534f', 0, 0, 0)

Line : 187
File : sessions.php