phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO r2ok_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('2a1b65d8037f6a9c7c2d43555cbb9ee7', -1, 1524207319, 1524207319, '3650082c', 2, 0, 0)

Line : 187
File : sessions.php