Subscription not kicking off for Property update when property value is Deleted vs. Cleared

We have a subscription setup from one viewpoint to another. Everything works fine for the subscription, except when a specific property value is Deleted, instead of Cleared, it will not generate a subscription to pass that now empty value on to the other viewpoint. Is there a way to fix this so even when a property value is Deleted it will kick off a subscription? If the value is Cleared out, using the Clear option, then the subscription will kick off. The specific property is the End Date property.