diff --git a/polymer.html b/polymer.html
index 5f4cbbc008..605a7afc19 100644
--- a/polymer.html
+++ b/polymer.html
@@ -72,7 +72,7 @@
       this._setupShady();
       this._registerHost();
       if (this._template) {
-        this._validateMixins();
+        this._validateApplyShim();
         // manage local dom
         this._poolContent();
         // host stack
diff --git a/src/lib/apply-shim.html b/src/lib/apply-shim.html
index 09b8f25a18..cfde273b2d 100644
--- a/src/lib/apply-shim.html
+++ b/src/lib/apply-shim.html
@@ -142,8 +142,10 @@
       // NOTE: since we use mixin, the map of properties is updated here
       // and this is what we want.
       combinedProps = Polymer.Base.mixin(mixinEntry.properties, mixinValues);
+      var currentProto = ApplyShim.__currentElementProto;
+      var currentElementName = currentProto && currentProto.is;
       for (var elementName in mixinEntry.dependants) {
-        if (elementName !== ApplyShim.__currentElementProto.is) {
+        if (elementName !== currentElementName) {
           mixinEntry.dependants[elementName].__mixinsInvalid = true;
         }
       }
@@ -181,7 +183,9 @@
     var mixinEntry = mapGet(mixinName);
     if (mixinEntry) {
       var currentProto = ApplyShim.__currentElementProto;
-      mixinEntry.dependants[currentProto.is] = currentProto;
+      if (currentProto) {
+        mixinEntry.dependants[currentProto.is] = currentProto;
+      }
       var p, parts, f;
       for (p in mixinEntry.properties) {
         f = fallbacks && fallbacks[p];
diff --git a/src/standard/x-styling.html b/src/standard/x-styling.html
index d4e5e4378d..bbdee7c2a7 100644
--- a/src/standard/x-styling.html
+++ b/src/standard/x-styling.html
@@ -74,7 +74,7 @@
           this._ownStylePropertyNames.length);
       },
 
-      _validateMixins: function() {
+      _validateApplyShim: function() {
         if (this.__mixinsInvalid) {
           // rerun apply shim
           Polymer.ApplyShim.transform(this._styles, this.__proto__);