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 ('c6391304e17f01a3896a5a30df011a60', -1, 1427794901, 1427794901, '36a1ea96', -4, 0, 0)

Line : 189
File : sessions.php