--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@@ -3752,16 +3752,19 @@ ScrollFrameHelper::DecideScrollableLayer
       nsLayoutUtils::GetDisplayPort(content, &displayPort, RelativeTo::ScrollFrame);
 
     if (usingDisplayPort) {
       // Override the dirty rectangle if the displayport has been set.
       *aVisibleRect = displayPort;
       if (!aBuilder->IsPartialUpdate() ||
           aBuilder->InInvalidSubtree()) {
         *aDirtyRect = displayPort;
+        if (aUsingDisplayPortInvalidRect) {
+          *aUsingDisplayPortInvalidRect = true;
+        }
       } else if (mOuter->HasOverrideDirtyRegion()) {
         nsRect* rect =
           mOuter->GetProperty(nsDisplayListBuilder::DisplayListBuildingDisplayPortRect());
         if (rect) {
           *aDirtyRect = *rect;
           if (aUsingDisplayPortInvalidRect) {
             *aUsingDisplayPortInvalidRect = true;
           }