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 ('3203d721f25588b7e1ac350bdd27305f', -1, 1529646068, 1529646068, '3650f777', -9, 0, 0)

Line : 187
File : sessions.php