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 ('7fe976b4133faa5d6cf8a92c26173e6b', -1, 1539827738, 1539827738, '36c60f14', 1, 0, 0)

Line : 187
File : sessions.php