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 ('4bed9ae3a2000166288a2fabed0996e6', -1, 1540361342, 1540361342, '365ca369', 2, 0, 0)

Line : 187
File : sessions.php