phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in) VALUES ('6f0cb238919ebcae659b7b2d9b081bb2', -1, 1409631261, 1409631261, '36eac855', 11, 0)

Line : 315
File : sessions.php