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 ('f6f2bf45cbccf45a4e858a8cf2aa6f8b', -1, 1513306222, 1513306222, '365acf4b', 7, 0, 0)

Line : 189
File : sessions.php