diff --git a/polymer-ui-theme-aware.html b/polymer-ui-theme-aware.html
index 6781235..e683c74 100644
--- a/polymer-ui-theme-aware.html
+++ b/polymer-ui-theme-aware.html
@@ -10,17 +10,20 @@
     PolymerUI = {
       validateTheme: function() {
         var theme = this.theme;
+        var defaultTheme = this.defaultTheme;
         if (!theme) {
           var p = this;
           while (p && !theme) {
             theme = p.getAttribute && p.getAttribute('theme');
+            defaultTheme = defaultTheme || p.defaultTheme;
             p = p.parentNode || p.host;
           }
         }
-        this.activeTheme = this.theme || theme;
+        this.activeTheme = this.theme || theme || defaultTheme;
       }
     };
     Polymer('polymer-ui-theme-aware', {
+      defaultTheme: '',
       activeTheme: '',
       validateTheme: PolymerUI.validateTheme,
       enteredView: function() {