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 ('97fd94eb5dd5c0b745e48aa87cfb6f62', -1, 1529823855, 1529823855, '365147db', 36, 0, 0)

Line : 187
File : sessions.php