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 ('74db73b6e5eb43d4538175096c655b76', -1, 1539726766, 1539726766, '36e11a2c', 15, 0, 0)

Line : 187
File : sessions.php