You probably need the 2 mm MAVIC spacer in addition to the Shimano spacer. MAVIC cassettes are 2 mm wider than 8, 9-speed Shimano cassettes, the 2 mm MAVIC spacer makes up the difference. The Shimano cassette is 1 mm narrower than the 8, 9-speed cassettes, the 1 mm Shimano spacer makes up the difference. So you need both.
Al