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 ('087ae96f39d7831d2d524dfe756f0c8a', -1, 1529638499, 1529638499, '36a2a59e', 2, 0, 0)

Line : 187
File : sessions.php