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 ('3bbe08d191e3b80305b95df9447b0a3a', -1, 1467360012, 1467360012, '36c655c4', -10, 0, 0)

Line : 201
File : sessions.php