When redeclaring a property, you can specify that the property has no default value, even if the inherited property specified one. 

To designate a property as having no default value, append the nodefault directive to the property's declaration. For example,

property FavoriteFlavor string nodefault;

__property int NewInteger = {nodefault};

When you declare a property for the first time, there is no need to include nodefault. The absence of a declared default value means that there is no default.