phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry 'ac1f1a408c9fa74946ac6666b12de1e0' for key 'PRIMARY'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('ac1f1a408c9fa74946ac6666b12de1e0', -1, 1516787503, 1516787503, '36e2295b', 2, 0, 0)

Line : 187
File : sessions.php