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 ('a3bccf307cdbf5448e2f1e174f9c216c', -1, 1397913753, 1397913753, '171414c3', 4, 0)

Line : 158
File : sessions.php