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 ('2011082c74c86b0e3e1d98597e3837e4', -1, 1713864198, 1713864198, '12de7dab', 7, 0, 0)

Line : 187
File : sessions.php