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 ('f9c36ef84d7f21434b93c12ee4f39d0e', -1, 1537351168, 1537351168, '36e0a68d', 3, 0, 0)

Line : 187
File : sessions.php