diff --git a/dom/html/ImageDocument.cpp b/dom/html/ImageDocument.cpp
index 7c32d44d8ba3..3a513883fbad 100644
--- a/dom/html/ImageDocument.cpp
+++ b/dom/html/ImageDocument.cpp
@@ -413,7 +413,7 @@ ImageDocument::RestoreImage()
   imageContent->UnsetAttr(kNameSpaceID_None, nsGkAtoms::width, true);
   imageContent->UnsetAttr(kNameSpaceID_None, nsGkAtoms::height, true);
   
-  if (mImageIsOverflowing) {
+  if (ImageIsOverflowing()) {
     SetModeClass(eOverflowing);
   }
   else {
@@ -441,7 +441,7 @@ ImageDocument::ToggleImageSize()
     ResetZoomLevel();
     RestoreImage();
   }
-  else if (mImageIsOverflowing) {
+  else if (ImageIsOverflowing()) {
     ResetZoomLevel();
     ShrinkToFit();
   }
@@ -579,7 +579,7 @@ ImageDocument::HandleEvent(nsIDOMEvent* aEvent)
       mShouldResize = false;
       RestoreImageTo(x, y);
     }
-    else if (mImageIsOverflowing) {
+    else if (ImageIsOverflowing()) {
       ShrinkToFit();
     }
   } else if (eventType.EqualsLiteral("load")) {
@@ -681,14 +681,14 @@ ImageDocument::CheckOverflowing(bool changeState)
     mVisibleHeight = nsPresContext::AppUnitsToFloatCSSPixels(visibleArea.height);
   }
 
-  bool imageWasOverflowing = mImageIsOverflowing;
-  mImageIsOverflowing =
-    mImageWidth > mVisibleWidth || mImageHeight > mVisibleHeight;
-  bool windowBecameBigEnough = imageWasOverflowing && !mImageIsOverflowing;
+  bool imageWasOverflowing = ImageIsOverflowing();
+  mImageIsOverflowingHorizontally = mImageWidth > mVisibleWidth;
+  mImageIsOverflowingVertically = mImageHeight > mVisibleHeight;
+  bool windowBecameBigEnough = imageWasOverflowing && !ImageIsOverflowing();
 
   if (changeState || mShouldResize || mFirstResize ||
       windowBecameBigEnough) {
-    if (mImageIsOverflowing && (changeState || mShouldResize)) {
+    if (ImageIsOverflowing() && (changeState || mShouldResize)) {
       ShrinkToFit();
     }
     else if (mImageIsResized || mFirstResize || windowBecameBigEnough) {
diff --git a/dom/html/ImageDocument.h b/dom/html/ImageDocument.h
index a35386975a65..039cd9b02d98 100644
--- a/dom/html/ImageDocument.h
+++ b/dom/html/ImageDocument.h
@@ -62,7 +62,7 @@ public:
   }
   bool ImageIsOverflowing() const
   {
-    return mImageIsOverflowing;
+    return mImageIsOverflowingHorizontally || mImageIsOverflowingVertically;
   }
   bool ImageIsResized() const
   {
@@ -118,7 +118,8 @@ protected:
 
   bool                          mResizeImageByDefault;
   bool                          mClickResizingEnabled;
-  bool                          mImageIsOverflowing;
+  bool                          mImageIsOverflowingHorizontally;
+  bool                          mImageIsOverflowingVertically;
   // mImageIsResized is true if the image is currently resized
   bool                          mImageIsResized;
   // mShouldResize is true if the image should be resized when it doesn't fit