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 ('7bb044418b2c9cdbe30104c30c6813c1', -1, 1513621738, 1513621738, '3652385f', -4, 0, 0)

Line : 193
File : sessions.php