isnull not working

I have the following SQL statement run by 2008 R2 version

,max(CASE 
	WHEN Rn = 3
	      THEN isnull(Name,'-')
			END) AS [Salesperson #3]

The expected result is to replace null with the character '-' but it shows in the Salesperson #3 field  'Null' value. Salesperson contains string, series of characters , or names such as Cameson Smith or Ali baba

How this can be resolved