diff --git a/gfx/layers/basic/BasicLayersImpl.cpp b/gfx/layers/basic/BasicLayersImpl.cpp
index de00ae807fa8..2551a9c2d6be 100644
--- a/gfx/layers/basic/BasicLayersImpl.cpp
+++ b/gfx/layers/basic/BasicLayersImpl.cpp
@@ -174,32 +174,6 @@ FillRectWithMask(DrawTarget* aDT,
   aDT->FillRect(aRect, SurfacePattern(aSurface, ExtendMode::CLAMP, Matrix(), aFilter), aOptions);
 }
 
-void
-FillWithMask(gfxContext* aContext, float aOpacity, Layer* aMaskLayer)
-{
-  AutoMaskData mask;
-  if (GetMaskData(aMaskLayer, &mask)) {
-    if (aOpacity < 1.0) {
-      aContext->PushGroup(gfxContentType::COLOR_ALPHA);
-      aContext->FillWithOpacity(aOpacity);
-      aContext->PopGroupToSource();
-      aContext->SetMatrix(ThebesMatrix(mask.GetTransform()));
-      aContext->Mask(mask.GetSurface());
-    } else {
-      aContext->Save();
-      aContext->Clip();
-      aContext->SetMatrix(ThebesMatrix(mask.GetTransform()));
-      aContext->Mask(mask.GetSurface());
-      aContext->NewPath();
-      aContext->Restore();
-    }
-    return;
-  }
-
-  // if there is no mask, just fill normally
-  aContext->FillWithOpacity(aOpacity);
-}
-
 BasicImplData*
 ToData(Layer* aLayer)
 {
diff --git a/gfx/layers/basic/BasicLayersImpl.h b/gfx/layers/basic/BasicLayersImpl.h
index 70039e978b2e..a9130460af63 100644
--- a/gfx/layers/basic/BasicLayersImpl.h
+++ b/gfx/layers/basic/BasicLayersImpl.h
@@ -94,7 +94,6 @@ void
 PaintWithMask(gfxContext* aContext, float aOpacity, Layer* aMaskLayer);
 
 // Fill the rect with the source, using a mask and opacity, if present
-void FillWithMask(gfxContext* aContext, float aOpacity, Layer* aMaskLayer);
 void
 FillRectWithMask(gfx::DrawTarget* aDT,
                  const gfx::Rect& aRect,