phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 'session_user_id'

INSERT INTO forum_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('1b26aa3edf1a813be5a2cdafa3a1d1c3', -1, 1539607817, 1539607817, '36c637a7', 0, 0, 0)

Line : 187
File : sessions.php