Cast BlockProxy to Block

HI! I am trying to somehow get MyBlock class instance from PropertyData.

I have tried:

propertyData.Value as MyBlock;

ProxyUtil.GetUnproxiedInstance( propertyData.Value);

((IProxyTargetAccessor) propertyData.Value).DynProxyGetTarget();

((MyBlock)propertyData.Value).CreateWritableClone ( );

They all return MyBlockProxy!

ProxyUtil.GetUnproxiedType ( propertyData.Value ); gives the correct type (MyBlock)

Is there a way to do this?