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 ('05d35c185d239635cfd254336e57f22d', -1, 1398056198, 1398056198, 'b8495755', -4, 0)

Line : 158
File : sessions.php