diff --git a/browser/devtools/netmonitor/netmonitor-view.js b/browser/devtools/netmonitor/netmonitor-view.js
index 00125227ca4b..b05776682577 100644
--- a/browser/devtools/netmonitor/netmonitor-view.js
+++ b/browser/devtools/netmonitor/netmonitor-view.js
@@ -337,7 +337,7 @@ RequestsMenuView.prototype = Heritage.extend(WidgetMethods, {
     this._registerLastRequestEnd(unixTime);
 
     // Append a network request item to this container.
-    let requestItem = this.push([menuView, aId], {
+    let requestItem = this.push([menuView, aId, ""], {
       attachment: {
         startedDeltaMillis: unixTime - this._firstRequestStartedMillis,
         startedMillis: unixTime,
@@ -368,7 +368,7 @@ RequestsMenuView.prototype = Heritage.extend(WidgetMethods, {
     // Create the element node for the network request item.
     let menuView = this._createMenuView(selected.method, selected.url);
 
-    let newItem = this.push([menuView], {
+    let newItem = this.push([menuView,, ""], {
       attachment: Object.create(selected, {
         isCustom: { value: true }
       })
diff --git a/browser/devtools/shared/widgets/ViewHelpers.jsm b/browser/devtools/shared/widgets/ViewHelpers.jsm
index 167f9e8710e9..b6b65d010a20 100644
--- a/browser/devtools/shared/widgets/ViewHelpers.jsm
+++ b/browser/devtools/shared/widgets/ViewHelpers.jsm
@@ -377,9 +377,13 @@ function Item(aOwnerView, aAttachment, aContents = []) {
   this.attachment = aAttachment;
 
   let [aLabel, aValue, aDescription] = aContents;
+  // Make sure the label and the value are always strings.
   this._label = aLabel + "";
   this._value = aValue + "";
-  this._description = (aDescription || "") + "";
+  // Make sure the description is also a string, but only if it's available.
+  if (aDescription !== undefined) {
+    this._description = aDescription + "";
+  }
 
   // Allow the insertion of prebuilt nodes, otherwise delegate the item view
   // creation to a widget.
@@ -499,7 +503,7 @@ Item.prototype = {
 
   _label: "",
   _value: "",
-  _description: "",
+  _description: undefined,
   _prebuiltTarget: null,
   _target: null,
   finalize: null,
@@ -663,9 +667,12 @@ this.WidgetMethods = {
     if (!selectedItem) {
       return false;
     }
+
+    let { _label: label, _value: value, _description: desc } = selectedItem;
     this._widget.removeAttribute("notice");
-    this._widget.setAttribute("label", selectedItem._label);
-    this._widget.setAttribute("tooltiptext", selectedItem._value);
+    this._widget.setAttribute("label", label);
+    this._widget.setAttribute("tooltiptext", desc !== undefined ? desc : value);
+
     return true;
   },