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 ('dc38d57d3ba00c7ec43421d065ea68ed', -1, 1414769360, 1414769360, '36a1ca6a', 39, 0, 0)

Line : 187
File : sessions.php