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 ('1b4c8567374f16a0e848f8994f53a1db', -1, 1540212058, 1540212058, '36e05922', -4, 0, 0)

Line : 187
File : sessions.php