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 ('04424c838c6a9a26f77b62625b37f2c3', -1, 1398036894, 1398036894, '43ca04e1', 23, 0)

Line : 158
File : sessions.php