--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -3048,16 +3048,17 @@ void nsWindow::SetTransparencyMode(nsTra
   nsWindow* window = GetTopLevelWindow(true);
   MOZ_ASSERT(window);
 
   if (!window || window->DestroyCalled()) {
       return;
   }
 
   if (nsWindowType::eWindowType_toplevel == window->mWindowType &&
+      mTransparencyMode != aMode &&
       !nsUXThemeData::CheckForCompositor()) {
       NS_WARNING("Cannot set transparency mode on top-level windows.");
       return;
   }
 
   window->SetWindowTranslucencyInner(aMode);
 }