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 ('3af36642471f3a418b31ae54994bec76', -1, 1398045607, 1398045607, '36d3bee8', -4, 0)

Line : 158
File : sessions.php