diff --git a/addon-sdk/source/lib/sdk/panel/utils.js b/addon-sdk/source/lib/sdk/panel/utils.js
index e0903f1970ba..56e8bd78dcf5 100644
--- a/addon-sdk/source/lib/sdk/panel/utils.js
+++ b/addon-sdk/source/lib/sdk/panel/utils.js
@@ -106,8 +106,10 @@ exports.close = close
 function resize(panel, width, height) {
   // Resize the iframe instead of using panel.sizeTo
   // because sizeTo doesn't work with arrow panels
-  panel.firstChild.style.width = width + "px";
-  panel.firstChild.style.height = height + "px";
+  if (panel.firstChild) {
+    panel.firstChild.style.width = width + "px";
+    panel.firstChild.style.height = height + "px";
+  }
 }
 exports.resize = resize
 
diff --git a/addon-sdk/source/test/test-panel.js b/addon-sdk/source/test/test-panel.js
index 34dd201097aa..13776e9dbc3e 100644
--- a/addon-sdk/source/test/test-panel.js
+++ b/addon-sdk/source/test/test-panel.js
@@ -254,6 +254,10 @@ exports["test Resize Panel"] = function(assert, done) {
       height: 10,
       width: 10,
       onMessage: function (message) {
+        // Make sure that attempting to resize a panel while it isn't
+        // visible doesn't cause an error.
+        panel.resize(1, 1);
+
         panel.show();
       },
       onShow: function () {
@@ -335,7 +339,7 @@ exports["test Several Show Hides"] = function(assert, done) {
   panel.show();
 };
 
-exports["test Anchor And Arrow"] = function(assert, done) {
+exports["test Anchor And Arrow"] = function*(assert, done) {
   let { loader } = LoaderWithHookedConsole(module, ignorePassingDOMNodeWarning);
   let { Panel } = loader.require('sdk/panel');