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 ('c3b71e969a3cbd20ce4cb2025d3f56d2', -1, 1529949073, 1529949073, '36c42a92', 45, 0, 0)

Line : 187
File : sessions.php