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 ('547ccba0ce3db80cd39e8046f0655f4c', -1, 1513621034, 1513621034, '3652385f', -52, 0, 0)

Line : 193
File : sessions.php