diff --git a/browser/devtools/markupview/markup-view.js b/browser/devtools/markupview/markup-view.js
index 3f059677be08..969f2852e21a 100644
--- a/browser/devtools/markupview/markup-view.js
+++ b/browser/devtools/markupview/markup-view.js
@@ -857,29 +857,33 @@ MarkupView.prototype = {
   },
 
   /**
-   * Retrieve the index of a child within its parent's children collection.
-   * @param aNode The NodeFront to find the index of.
+   * Replace the outerHTML of any node displayed in the inspector with
+   * some other HTML code
+   * @param aNode node which outerHTML will be replaced.
    * @param newValue The new outerHTML to set on the node.
-   * @param oldValue The old outerHTML that will be reverted to find the index of.
-   * @returns A promise that will be resolved with the integer index.
-   *          If the child cannot be found, returns -1
+   * @param oldValue The old outerHTML that will be used if the user undos the update.
+   * @returns A promise that will resolve when the outer HTML has been updated.
    */
   updateNodeOuterHTML: function(aNode, newValue, oldValue) {
-    let container = this.getContainer(aNode);
+    let container = this._containers.get(aNode);
     if (!container) {
-      return;
+      return promise.reject();
     }
 
+    let def = promise.defer();
+
     this.getNodeChildIndex(aNode).then((i) => {
       this._outerHTMLChildIndex = i;
       this._outerHTMLNode = aNode;
 
       container.undo.do(() => {
-        this.walker.setOuterHTML(aNode, newValue);
+        this.walker.setOuterHTML(aNode, newValue).then(def.resolve, def.reject);
       }, () => {
-        this.walker.setOuterHTML(aNode, oldValue);
+        this.walker.setOuterHTML(aNode, oldValue).then(def.resolve, def.reject);
       });
     });
+
+    return def.promise;
   },
 
   /**