diff --git a/src/ShadowCSS.js b/src/ShadowCSS.js
index e975434..8851e07 100644
--- a/src/ShadowCSS.js
+++ b/src/ShadowCSS.js
@@ -156,6 +156,8 @@ var ShadowCSS = {
     this.insertPolyfillDirectives(def.rootStyles);
     this.insertPolyfillRules(def.rootStyles);
     var cssText = this.stylesToShimmedCssText(def.scopeStyles, name);
+    // note: we only need to do rootStyles since these are unscoped.
+    cssText += this.extractPolyfillUnscopedRules(def.rootStyles);
     // provide shimmedStyle for user extensibility
     def.shimmedStyle = cssTextToStyle(cssText);
     if (root) {
@@ -263,6 +265,37 @@ var ShadowCSS = {
     r += cssText.substring(l, cssText.length);
     return r;
   },
+  /*
+   * Process styles to add rules which will only apply under the polyfill
+   * and do not process via CSSOM. (CSSOM is destructive to rules on rare 
+   * occasions, e.g. -webkit-calc on Safari.)
+   * For example, we convert this rule:
+   * 
+   * (comment start) @polyfill-unscoped-rule menu-item { 
+   * ... } (comment end)
+   * 
+   * to this:
+   * 
+   * menu-item {...}
+   *
+  **/
+  extractPolyfillUnscopedRules: function(styles) {
+    var cssText = '';
+    if (styles) {
+      Array.prototype.forEach.call(styles, function(s) {
+        cssText += this.extractPolyfillUnscopedRulesFromCssText(
+            s.textContent) + '\n\n';
+      }, this);
+    }
+    return cssText;
+  },
+  extractPolyfillUnscopedRulesFromCssText: function(cssText) {
+    var r = '', l = 0, matches;
+    while (matches = cssPolyfillUnscopedRuleCommentRe.exec(cssText)) {
+      r += matches[1].slice(0, -1) + '\n\n';
+    }
+    return r;
+  },
   // apply @host and scope shimming
   stylesToShimmedCssText: function(styles, name) {
     return this.shimAtHost(styles, name) + this.shimScoping(styles, name);
@@ -434,6 +467,7 @@ var hostRuleRe = /@host[^{]*{(([^}]*?{[^{]*?}[\s\S]*?)+)}/gim,
     cssCommentRe = /\/\*[^*]*\*+([^/*][^*]*\*+)*\//gim,
     cssPolyfillCommentRe = /\/\*\s*@polyfill ([^*]*\*+([^/*][^*]*\*+)*\/)([^{]*?){/gim,
     cssPolyfillRuleCommentRe = /\/\*\s@polyfill-rule([^*]*\*+([^/*][^*]*\*+)*)\//gim,
+    cssPolyfillUnscopedRuleCommentRe = /\/\*\s@polyfill-unscoped-rule([^*]*\*+([^/*][^*]*\*+)*)\//gim,
     cssPseudoRe = /::(x-[^\s{,(]*)/gim,
     selectorReSuffix = '([>\\s~+\[.,{:][\\s\\S]*)?$',
     hostRe = /@host/gim,
diff --git a/test/html/styling/polyfill-rule.html b/test/html/styling/polyfill-rule.html
index d04e2ec..a66d2a1 100644
--- a/test/html/styling/polyfill-rule.html
+++ b/test/html/styling/polyfill-rule.html
@@ -16,12 +16,17 @@
   <x-foo>
     <div class="zonk">red?</div>
   </x-foo>
- 
+  <div class="unscoped">unscoped</div>
   <template id="x-foo">
     <style>
       /* @polyfill-rule :host > .zonk {
         background: red;
       } */
+
+      /* @polyfill-unscoped-rule .unscoped {
+        background: black;
+        color: white;
+      } */
     </style>
     <content></content>
   </template>
@@ -30,13 +35,16 @@
     XFoo = register('x-foo', '', HTMLElement.prototype);
     
     document.addEventListener('WebComponentsReady', function() {
-      setTimeout(function() {
+      //setTimeout(function() {
         var foo = document.querySelector('x-foo');
         fooDiv = foo.firstElementChild;
         chai.assert.equal(getComputedStyle(fooDiv).backgroundColor, 
           'rgb(255, 0, 0)', '@polyfill styles are applied');
+        var unscoped = document.querySelector('.unscoped');
+        chai.assert.equal(getComputedStyle(unscoped).backgroundColor, 
+          'rgb(0, 0, 0)', '@polyfill-unscoped-rule styles are applied');
         done();
-      });
+      //});
     });
   </script>