--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -479,17 +479,21 @@ nsStyleBorder::CalcDifference(const nsSt
     }
   }
 
   if (mBorderRadius != aNewData.mBorderRadius ||
       !mBorderColors != !aNewData.mBorderColors) {
     return nsChangeHint_RepaintFrame;
   }
 
-  if (IsBorderImageLoaded() || aNewData.IsBorderImageLoaded()) {
+  // Loading status of the border image can be accessed in main thread only
+  // while CalcDifference might be executed on a background thread. As a
+  // result, we have to check mBorderImage* fields even before border image was
+  // actually loaded.
+  if (!mBorderImageSource.IsEmpty() || !aNewData.mBorderImageSource.IsEmpty()) {
     if (mBorderImageSource  != aNewData.mBorderImageSource  ||
         mBorderImageRepeatH != aNewData.mBorderImageRepeatH ||
         mBorderImageRepeatV != aNewData.mBorderImageRepeatV ||
         mBorderImageSlice   != aNewData.mBorderImageSlice   ||
         mBorderImageFill    != aNewData.mBorderImageFill    ||
         mBorderImageWidth   != aNewData.mBorderImageWidth) {
       return nsChangeHint_RepaintFrame;
     }
@@ -508,19 +512,17 @@ nsStyleBorder::CalcDifference(const nsSt
 
   // mBorder is the specified border value.  Changes to this don't
   // need any change processing, since we operate on the computed
   // border values instead.
   if (mBorder != aNewData.mBorder) {
     return nsChangeHint_NeutralChange;
   }
 
-  // mBorderImage* fields are checked only when border image was
-  // actualy loaded. But we need to return neutral change even when
-  // they are not actually used.
+  // mBorderImage* fields are checked only when border-image is not 'none'.
   if (mBorderImageSource  != aNewData.mBorderImageSource  ||
       mBorderImageRepeatH != aNewData.mBorderImageRepeatH ||
       mBorderImageRepeatV != aNewData.mBorderImageRepeatV ||
       mBorderImageSlice   != aNewData.mBorderImageSlice   ||
       mBorderImageFill    != aNewData.mBorderImageFill    ||
       mBorderImageWidth   != aNewData.mBorderImageWidth) {
     return nsChangeHint_NeutralChange;
   }