diff --git a/widget/gtk/WindowSurfaceProvider.cpp b/widget/gtk/WindowSurfaceProvider.cpp
index faf147a80a4a1..b346f0783d101 100644
--- a/widget/gtk/WindowSurfaceProvider.cpp
+++ b/widget/gtk/WindowSurfaceProvider.cpp
@@ -52,6 +52,16 @@ WindowSurfaceProvider::WindowSurfaceProvider()
 {
 }
 
+WindowSurfaceProvider::~WindowSurfaceProvider() {
+#ifdef MOZ_WAYLAND
+  MOZ_DIAGNOSTIC_ASSERT(!mWidget,
+                        "nsWindow reference is still live, we're leaking it!");
+#endif
+#ifdef MOZ_X11
+  MOZ_DIAGNOSTIC_ASSERT(!mXWindow, "mXWindow should be released on quit!");
+#endif
+}
+
 #ifdef MOZ_WAYLAND
 void WindowSurfaceProvider::Initialize(RefPtr<nsWindow> aWidget) {
   mWindowSurfaceValid = false;
diff --git a/widget/gtk/WindowSurfaceProvider.h b/widget/gtk/WindowSurfaceProvider.h
index 353fa82f708fb..a040bbe3957f1 100644
--- a/widget/gtk/WindowSurfaceProvider.h
+++ b/widget/gtk/WindowSurfaceProvider.h
@@ -36,7 +36,7 @@ class GtkCompositorWidget;
 class WindowSurfaceProvider final {
  public:
   WindowSurfaceProvider();
-  ~WindowSurfaceProvider() = default;
+  ~WindowSurfaceProvider();
 
   /**
    * Initializes the WindowSurfaceProvider by giving it the window
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index 4e96f8218784a..fac9ea1cfef5b 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -615,6 +615,10 @@ void nsWindow::Destroy() {
 
   DestroyLayerManager();
 
+  // mSurfaceProvider holds reference to this nsWindow so we need to explicitly
+  // clear it here to avoid nsWindow leak.
+  mSurfaceProvider.CleanupResources();
+
   g_signal_handlers_disconnect_by_data(gtk_settings_get_default(), this);
 
   if (mIMContext) {