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 ('ce9929832b38d5f3fd67593a3309968d', -1, 1417041534, 1417041534, '36d361f2', 20, 0, 0)

Line : 187
File : sessions.php