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 ('b985d013cc80381de8f510224560c83e', -1, 1529693389, 1529693389, '36a7e644', 4, 0, 0)

Line : 187
File : sessions.php