diff --git a/src/wrappers/Window.js b/src/wrappers/Window.js
index f2abbdd..2c00323 100644
--- a/src/wrappers/Window.js
+++ b/src/wrappers/Window.js
@@ -11,6 +11,7 @@
   var unwrap = scope.unwrap;
   var unwrapIfNeeded = scope.unwrapIfNeeded;
   var wrap = scope.wrap;
+  var renderAllPending = scope.renderAllPending;
 
   var OriginalWindow = window.Window;
 
@@ -21,6 +22,7 @@
 
   var originalGetComputedStyle = window.getComputedStyle;
   OriginalWindow.prototype.getComputedStyle = function(el, pseudo) {
+    renderAllPending();
     return originalGetComputedStyle.call(this || window, unwrapIfNeeded(el),
                                          pseudo);
   };
diff --git a/test/js/Window.js b/test/js/Window.js
index 1f9a1f1..4778cd4 100644
--- a/test/js/Window.js
+++ b/test/js/Window.js
@@ -56,4 +56,15 @@ suite('Window', function() {
     assert.isTrue(cs != null);
   });
 
+  test('getComputedStyleShadow', function() {
+    var host = document.createElement('div');
+    var root = host.createShadowRoot();
+    var elt = document.createElement('div');
+    root.appendChild(elt);
+    document.body.appendChild(host);
+    elt.style.padding = '4px';
+    assert.equal(getComputedStyle(elt).paddingLeft, '4px');
+    document.body.removeChild(host);
+  });
+
 });