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, session_admin) VALUES ('58dd0e51f3e7092f55933bf976ab7454', -1, 1422785358, 1422785358, '36d3ee2f', -1, 0, 0)

Line : 187
File : sessions.php