Assume objects are always dirty.

src/lib/bind/accessors.html

@@ -45,10 +45,7 @@
       _propertySetter: function(property, value, effects, fromAbove,
                                 origin, originalProperty) {
         var old = this.__data__[property];
-        // NaN is always not equal to itself,
-        // if old and value are both NaN we treat them as equal
-        // x === x is 10x faster, and equivalent to !isNaN(x)
-        if (old !== value && (old === old || value === value)) {
+        if (this._isPropertyDirty(property, value, old) !== false) {
           this.__data__[property] = value;
           if (typeof value == 'object') {
             this._clearPath(property);
@@ -64,6 +61,14 @@
         return old;
       },
 
+      _isPropertyDirty: function(property, value, old) {
+        // NaN is always not equal to itself,
+        // if old and value are both NaN we treat them as equal
+        // x === x is 10x faster, and equivalent to !isNaN(x)
+        return (old !== value && (old === old || value === value)) ||
+               typeof value == 'object';
+      },
+
       // Called during _applyConfig (well-known downward data-flow hot path)
       // in order to avoid firing notify events
       // TODO(kschaaf): downward bindings (e.g. _applyEffectValue) should also

src/standard/notify-path.html

@@ -87,15 +87,11 @@
         }
       },
 
-      // Note: this implemetation only accepts key-based array paths
+      // Note: this implementation only accepts key-based array paths
       _notifyPath: function(path, value, fromAbove, origin, originalProperty) {
         // All path/value pairs are cached on `this.__data__`
         var old = this.__data__[path];
-        // manual dirty checking for now...
-        // NaN is always not equal to itself,
-        // if old and value are both NaN we treat them as equal
-        // x === x is 10x faster, and equivalent to !isNaN(x)
-        if (old !== value && (old === old || value === value)) {
+        if (this._isPropertyDirty(path, value, old) !== false) {
           this.__data__[path] = value;
           if (typeof value == 'object') {
             this._clearPath(path);