Revoke Connect Guest User

I've used the following:
EXEC sp_MSforeachdb 'USE [?];
REVOKE CONNECT FROM GUEST;'
GO

And this is what I get:
Msg 15182, Level 16, State 1, Line 2
Cannot disable access to the guest user in master or tempdb.
Msg 15182, Level 16, State 1, Line 2
Cannot disable access to the guest user in master or tempdb.
Msg 15151, Level 16, State 1, Line 2
Cannot find the user 'GUEST', because it does not exist or you do not have permission.
Msg 15151, Level 16, State 1, Line 2
Cannot find the user 'GUEST', because it does not exist or you do not have permission.
Msg 15151, Level 16, State 1, Line 2
Cannot find the user 'GUEST', because it does not exist or you do not have permission.

When I do this:
EXEC sp_MSforeachdb 'USE [?];
SELECT ''[?]'' AS DBName,* FROM sysusers;'
GO

The guest sid for all tables shows 0x00, is this the reason I get above errors?