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 ('552452b3c525ccf19fd3606c8f627b2d', -1, 1416771018, 1416771018, '36cc497e', 45, 0, 0)

Line : 169
File : sessions.php