diff --git a/mobile/android/base/gfx/ViewportMetrics.java b/mobile/android/base/gfx/ViewportMetrics.java
index e50e160d504f..a9a48ab20b10 100644
--- a/mobile/android/base/gfx/ViewportMetrics.java
+++ b/mobile/android/base/gfx/ViewportMetrics.java
@@ -236,17 +236,17 @@ public class ViewportMetrics {
 
     public String toJSON() {
         try {
-            return new JSONStringer().object()
-                .key("x").value(mViewportRect.left)
-                .key("y").value(mViewportRect.top)
-                .key("width").value(mViewportRect.width())
-                .key("height").value(mViewportRect.height())
-                .key("pageWidth").value(mPageSize.width)
-                .key("pageHeight").value(mPageSize.height)
-                .key("offsetX").value(mViewportOffset.x)
-                .key("offsetY").value(mViewportOffset.y)
-                .key("zoom").value(mZoomFactor)
-                .endObject().toString();
+            JSONStringer object = new JSONStringer().object();
+            object.key("zoom").value(mZoomFactor);
+            object.key("offsetY").value(mViewportOffset.y);
+            object.key("offsetX").value(mViewportOffset.x);
+            object.key("pageHeight").value(mPageSize.height);
+            object.key("pageWidth").value(mPageSize.width);
+            object.key("height").value(mViewportRect.height());
+            object.key("width").value(mViewportRect.width());
+            object.key("y").value(mViewportRect.top);
+            object.key("x").value(mViewportRect.left);
+            return object.endObject().toString();
         } catch (JSONException je) {
             Log.e(LOGTAG, "Error serializing viewportmetrics", je);
             return "";
diff --git a/mobile/android/chrome/content/browser.js b/mobile/android/chrome/content/browser.js
index 351c5e7be160..2884e3502268 100644
--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -1160,10 +1160,10 @@ Tab.prototype = {
 
   get viewport() {
     // Update the viewport to current dimensions
-    this._viewport.x = this.browser.contentWindow.scrollX +
-                       this.viewportExcess.x;
-    this._viewport.y = this.browser.contentWindow.scrollY +
-                       this.viewportExcess.y;
+    this._viewport.x = (this.browser.contentWindow.scrollX +
+                        this.viewportExcess.x) || 0;
+    this._viewport.y = (this.browser.contentWindow.scrollY +
+                        this.viewportExcess.y) || 0;
 
     // Transform coordinates based on zoom
     this._viewport.x = Math.round(this._viewport.x * this._viewport.zoom);
@@ -1192,8 +1192,8 @@ Tab.prototype = {
   updateViewport: function(aReset) {
     let win = this.browser.contentWindow;
     let zoom = (aReset ? this.getDefaultZoomLevel() : this._viewport.zoom);
-    let xpos = (aReset ? win.scrollX * zoom : this._viewport.x);
-    let ypos = (aReset ? win.scrollY * zoom : this._viewport.y);
+    let xpos = ((aReset && win) ? win.scrollX * zoom : this._viewport.x);
+    let ypos = ((aReset && win) ? win.scrollY * zoom : this._viewport.y);
 
     this.viewportExcess = { x: 0, y: 0 };
     this.viewport = { x: xpos, y: ypos,