--- a/layout/svg/nsSVGIntegrationUtils.cpp
+++ b/layout/svg/nsSVGIntegrationUtils.cpp
@@ -415,46 +415,31 @@ public:
   }
 
 private:
   nsDisplayListBuilder* mBuilder;
   LayerManager* mLayerManager;
   nsPoint mOffset;
 };
 
-/**
- * Returns true if any of the masks is an image mask (and not an SVG mask).
- */
-static bool
-HasNonSVGMask(const nsTArray<nsSVGMaskFrame*>& aMaskFrames)
-{
-  for (size_t i = 0; i < aMaskFrames.Length() ; i++) {
-    nsSVGMaskFrame *maskFrame = aMaskFrames[i];
-    if (!maskFrame) {
-      return true;
-    }
-  }
-
-  return false;
-}
-
 typedef nsSVGIntegrationUtils::PaintFramesParams PaintFramesParams;
 
 /**
  * Paint css-positioned-mask onto a given target(aMaskDT).
  */
 static DrawResult
 PaintMaskSurface(const PaintFramesParams& aParams,
                  DrawTarget* aMaskDT, float aOpacity, nsStyleContext* aSC,
                  const nsTArray<nsSVGMaskFrame*>& aMaskFrames,
                  const gfxMatrix& aMaskSurfaceMatrix,
                  const nsPoint& aOffsetToUserSpace)
 {
   MOZ_ASSERT(aMaskFrames.Length() > 0);
   MOZ_ASSERT(aMaskDT->GetFormat() == SurfaceFormat::A8);
+  MOZ_ASSERT(aOpacity == 1.0 || aMaskFrames.Length() == 1);
 
   const nsStyleSVGReset *svgReset = aSC->StyleSVGReset();
   gfxMatrix cssPxToDevPxMatrix =
     nsSVGIntegrationUtils::GetCSSPxToDevPxMatrix(aParams.frame);
 
   nsPresContext* presContext = aParams.frame->PresContext();
   gfxPoint devPixelOffsetToUserSpace =
     nsLayoutUtils::PointToGfxPoint(aOffsetToUserSpace,
@@ -504,17 +489,18 @@ PaintMaskSurface(const PaintFramesParams
       nsRenderingContext rc(maskContext);
       nsCSSRendering::PaintBGParams  params =
         nsCSSRendering::PaintBGParams::ForSingleLayer(*presContext,
                                                       rc, aParams.dirtyRect,
                                                       aParams.borderArea,
                                                       aParams.frame,
                                                       aParams.builder->GetBackgroundPaintFlags() |
                                                       nsCSSRendering::PAINTBG_MASK_IMAGE,
-                                                      i, compositionOp);
+                                                      i, compositionOp,
+                                                      aOpacity);
 
       result =
         nsCSSRendering::PaintStyleImageLayerWithSC(params, aSC,
                                               *aParams.frame->StyleBorder());
       if (result != DrawResult::SUCCESS) {
         return result;
       }
     }
@@ -575,20 +561,21 @@ CreateAndPaintMaskSurface(const PaintFra
   RefPtr<DrawTarget> maskDT =
       ctx.GetDrawTarget()->CreateSimilarDrawTarget(maskSurfaceRect.Size(),
                                                    SurfaceFormat::A8);
   if (!maskDT || !maskDT->IsValid()) {
     paintResult.result = DrawResult::TEMPORARY_ERROR;
     return paintResult;
   }
 
-  // Set aAppliedOpacity as true only if all mask layers are svg mask.
-  // In this case, we will apply opacity into the final mask surface, so the
-  // caller does not need to apply it again.
-  paintResult.opacityApplied = !HasNonSVGMask(aMaskFrames);
+  // We can paint mask along with opacity only if
+  // 1. There is only one mask, or
+  // 2. No overlap among masks.
+  // Collision detect in #2 is not that trivial, we only accept #1 here.
+  paintResult.opacityApplied = (aMaskFrames.Length() == 1);
 
   // Set context's matrix on maskContext, offset by the maskSurfaceRect's
   // position. This makes sure that we combine the masks in device space.
   gfxMatrix maskSurfaceMatrix =
     ctx.CurrentMatrix() * gfxMatrix::Translation(-aParams.maskRect.TopLeft());
 
   paintResult.result = PaintMaskSurface(aParams, maskDT,
                                         paintResult.opacityApplied