Menu Icon too big after updating to iOS 8.2 and Xamarin.iOS 8.8.1

Hi,

I updated iOS to 8.2, Xamarin.iOS to 8.8.1 and XCode to 6.2. One of the consequences of these updates is that the icon for the slider menu is now bigger while my image resource remains the same. How can I control the size of this icon?
Tks.

François