diff --git a/widget/src/windows/nsWindow.cpp b/widget/src/windows/nsWindow.cpp
index af40e5e1d814..3f31ccca8e1e 100644
--- a/widget/src/windows/nsWindow.cpp
+++ b/widget/src/windows/nsWindow.cpp
@@ -2227,6 +2227,29 @@ HasDescendantWindowOutsideRect(DWORD aThisThreadID, HWND aWnd,
   return PR_FALSE;
 }
 
+static void
+InvalidateRgnInWindowSubtree(HWND aWnd, HRGN aRgn, HRGN aTmpRgn)
+{
+  RECT clientRect;
+  ::GetClientRect(aWnd, &clientRect);
+  ::SetRectRgn(aTmpRgn, clientRect.left, clientRect.top,
+               clientRect.right, clientRect.bottom);
+  if (::CombineRgn(aTmpRgn, aTmpRgn, aRgn, RGN_AND) == NULLREGION) {
+    return;
+  }
+
+  ::InvalidateRgn(aWnd, aTmpRgn, FALSE);
+
+  for (HWND child = ::GetWindow(aWnd, GW_CHILD); child;
+       child = ::GetWindow(child, GW_HWNDNEXT)) {
+    POINT pt = { 0, 0 };
+    ::MapWindowPoints(child, aWnd, &pt, 1);
+    ::OffsetRgn(aRgn, -pt.x, -pt.y);
+    InvalidateRgnInWindowSubtree(child, aRgn, aTmpRgn);
+    ::OffsetRgn(aRgn, pt.x, pt.y);
+  }
+}
+
 void
 nsWindow::Scroll(const nsIntPoint& aDelta,
                  const nsTArray<nsIntRect>& aDestRects,
@@ -2362,7 +2385,11 @@ nsWindow::Scroll(const nsIntPoint& aDelta,
     // it.
     ::SetRectRgn(destRgn, destRect.x, destRect.y, destRect.XMost(), destRect.YMost());
     ::CombineRgn(updateRgn, updateRgn, destRgn, RGN_AND);
-    ::InvalidateRgn(mWnd, updateRgn, FALSE);
+    if (flags & SW_SCROLLCHILDREN) {
+      InvalidateRgnInWindowSubtree(mWnd, updateRgn, destRgn);
+    } else {
+      ::InvalidateRgn(mWnd, updateRgn, FALSE);
+    }
   }
 
   ::DeleteObject((HGDIOBJ)updateRgn);