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 ('da3acbd28a5f7c457d13a54a8d716640', -1, 1467360106, 1467360106, '36c655c4', 0, 0, 0)

Line : 201
File : sessions.php