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 ('2be20380a1510ccb081ea06c21cbaa17', -1, 1540320215, 1540320215, '36c6d41e', 6, 0, 0)

Line : 187
File : sessions.php