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 ('50ab2d6cd3c48992a5b8f43973f8ef8f', -1, 1524205664, 1524205664, '3650082c', 2, 0, 0)

Line : 187
File : sessions.php