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, session_admin) VALUES ('4f4198eebddc1d7fe8b86667e4aa8a0b', -1, 1506346318, 1506346318, '6b1676f2', 12, 0, 0)

Line : 187
File : sessions.php