--- a/browser/components/customizableui/src/CustomizableUI.jsm
+++ b/browser/components/customizableui/src/CustomizableUI.jsm
@@ -1077,26 +1077,25 @@ let CustomizableUIInternal = {
       throw new Error("buildWidget was passed a non-widget to build.");
     }
 
     LOG("Building " + aWidget.id + " of type " + aWidget.type);
 
     let node;
     if (aWidget.type == "custom") {
       if (aWidget.onBuild) {
-        try {
-          node = aWidget.onBuild(aDocument);
-        } catch (ex) {
-          ERROR("Custom widget with id " + aWidget.id + " threw an error: " + ex.message);
-        }
+        node = aWidget.onBuild(aDocument);
       }
       if (!node || !(node instanceof aDocument.defaultView.XULElement))
         ERROR("Custom widget with id " + aWidget.id + " does not return a valid node");
     }
     else {
+      if (aWidget.onBeforeCreated) {
+        aWidget.onBeforeCreated(aDocument);
+      }
       node = aDocument.createElementNS(kNSXUL, "toolbarbutton");
 
       node.setAttribute("id", aWidget.id);
       node.setAttribute("widget-id", aWidget.id);
       node.setAttribute("widget-type", aWidget.type);
       if (aWidget.disabled) {
         node.setAttribute("disabled", true);
       }
@@ -1966,16 +1965,17 @@ let CustomizableUIInternal = {
     if ("type" in aData && gSupportedWidgetTypes.has(aData.type)) {
       widget.type = aData.type;
     } else {
       widget.type = "button";
     }
 
     widget.disabled = aData.disabled === true;
 
+    this.wrapWidgetEventHandler("onBeforeCreated", widget);
     this.wrapWidgetEventHandler("onClick", widget);
     this.wrapWidgetEventHandler("onCreated", widget);
 
     if (widget.type == "button") {
       widget.onCommand = typeof aData.onCommand == "function" ?
                            aData.onCommand :
                            null;
     } else if (widget.type == "view") {
@@ -2723,16 +2723,22 @@ this.CustomizableUI = {
    *                  'custom' - for fine-grained control over the creation
    *                             of the widget.
    * - viewId:        Only useful for views (and required there): the id of the
    *                  <panelview> that should be shown when clicking the widget.
    * - onBuild(aDoc): Only useful for custom widgets (and required there); a
    *                  function that will be invoked with the document in which
    *                  to build a widget. Should return the DOM node that has
    *                  been constructed.
+   * - onBeforeCreated(aDoc): Attached to all non-custom widgets; a function
+   *                  that will be invoked before the widget gets a DOM node
+   *                  constructed, passing the document in which that will happen.
+   *                  This is useful especially for 'view' type widgets that need
+   *                  to construct their views on the fly (e.g. from bootstrapped
+   *                  add-ons)
    * - onCreated(aNode): Attached to all widgets; a function that will be invoked
    *                  whenever the widget has a DOM node constructed, passing the
    *                  constructed node as an argument.
    * - onCommand(aEvt): Only useful for button widgets; a function that will be
    *                    invoked when the user activates the button.
    * - onClick(aEvt): Attached to all widgets; a function that will be invoked
    *                  when the user clicks the widget.
    * - onViewShowing(aEvt): Only useful for views; a function that will be

--- a/browser/components/customizableui/test/browser.ini
+++ b/browser/components/customizableui/test/browser.ini
@@ -69,9 +69,10 @@ skip-if = os == "linux"
 [browser_968565_insert_before_hidden_items.js]
 [browser_969427_recreate_destroyed_widget_after_reset.js]
 [browser_969661_character_encoding_navbar_disabled.js]
 [browser_970511_undo_restore_default.js]
 [browser_972267_customizationchange_events.js]
 [browser_973932_addonbar_currentset.js]
 [browser_975719_customtoolbars_behaviour.js]
 [browser_978084_dragEnd_after_move.js]
+[browser_981418-widget-onbeforecreated-handler.js]
 [browser_panel_toggle.js]

new file mode 100644
--- /dev/null
+++ b/browser/components/customizableui/test/browser_981418-widget-onbeforecreated-handler.js
@@ -0,0 +1,90 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+const kWidgetId = 'test-981418-widget-onbeforecreated';
+
+// Should be able to add broken view widget
+add_task(function testAddOnBeforeCreatedWidget() {
+  let viewShownDeferred = Promise.defer();
+  let onBeforeCreatedCalled = false;
+  let widgetSpec = {
+    id: kWidgetId,
+    type: 'view',
+    viewId: kWidgetId + 'idontexistyet',
+    onBeforeCreated: function(doc) {
+      let view = doc.createElement("panelview");
+      view.id = kWidgetId + 'idontexistyet';
+      let label = doc.createElement("label");
+      label.setAttribute("value", "Hello world");
+      label.className = 'panel-subview-header';
+      view.appendChild(label);
+      document.getElementById("PanelUI-multiView").appendChild(view);
+      onBeforeCreatedCalled = true;
+    },
+    onViewShowing: function() {
+      viewShownDeferred.resolve();
+    }
+  };
+
+  let noError = true;
+  try {
+    CustomizableUI.createWidget(widgetSpec);
+    CustomizableUI.addWidgetToArea(kWidgetId, CustomizableUI.AREA_NAVBAR);
+  } catch (ex) {
+    Cu.reportError(ex);
+    noError = false;
+  }
+  ok(noError, "Should not throw an exception trying to add the widget.");
+  ok(onBeforeCreatedCalled, "onBeforeCreated should have been called");
+
+  let widgetNode = document.getElementById(kWidgetId);
+  ok(widgetNode, "Widget should exist");
+  if (widgetNode) {
+    try {
+      widgetNode.click();
+
+      let shownTimeout = setTimeout(() => viewShownDeferred.reject("Panel not shown within 20s"), 20000);
+      yield viewShownDeferred.promise;
+      clearTimeout(shownTimeout);
+      ok(true, "Found view shown");
+
+      let tempPanel = document.getElementById("customizationui-widget-panel");
+      let panelHiddenPromise = promisePanelElementHidden(window, tempPanel);
+      tempPanel.hidePopup();
+      yield panelHiddenPromise;
+
+      CustomizableUI.addWidgetToArea(kWidgetId, CustomizableUI.AREA_PANEL);
+      yield PanelUI.show();
+
+      viewShownDeferred = Promise.defer();
+      widgetNode.click();
+
+      shownTimeout = setTimeout(() => viewShownDeferred.reject("Panel not shown within 20s"), 20000);
+      yield viewShownDeferred.promise;
+      clearTimeout(shownTimeout);
+      ok(true, "Found view shown");
+
+      let panelHidden = promisePanelHidden(window);
+      PanelUI.hide();
+      yield panelHidden;
+    } catch (ex) {
+      ok(false, "Unexpected exception (like a timeout for one of the yields) " +
+                "when testing view widget.");
+    }
+  }
+
+  noError = true;
+  try {
+    CustomizableUI.destroyWidget(kWidgetId);
+  } catch (ex) {
+    Cu.reportError(ex);
+    noError = false;
+  }
+  ok(noError, "Should not throw an exception trying to remove the broken view widget.");
+});
+
+add_task(function asyncCleanup() {
+  yield resetCustomization();
+});