phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('6dff064b92f955101072a19f41556a91', -1, 1430217176, 1430217176, '32101f3d', -1, 0, 0)

Line : 187
File : sessions.php