phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('9a2468483882b92165d61888fee656d9', -1, 1531913160, 1531913160, 'c0a865fd', -1, 0, 0)

Line : 187
File : sessions.php