phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in) VALUES ('93cd834f2a12274e3e7ed03203d2e49a', -1, 1414021872, 1414021872, 'ae816764', 42, 0)

Line : 158
File : sessions.php