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 ('3631bf7fd02399d378eeb42a6c63dc6f', -1, 1397947573, 1397947573, '1714951b', 14, 0)

Line : 158
File : sessions.php