--- a/widget/gtk/WindowSurfaceProvider.cpp
+++ b/widget/gtk/WindowSurfaceProvider.cpp
@@ -51,17 +51,17 @@ void WindowSurfaceProvider::Initialize(
   mXVisual = aVisual;
   mXDepth = aDepth;
   mIsX11Display = true;
 }
 
 #ifdef MOZ_WAYLAND
 void WindowSurfaceProvider::Initialize(nsWindow *aWidget)
 {
-  MOZ_ASSERT(!aWidget->IsX11Display(),
+  MOZ_ASSERT(aWidget->GetWaylandDisplay(),
              "We are supposed to have a Wayland display!");
 
   mWidget = aWidget;
   mIsX11Display = false;
 }
 #endif
 
 void WindowSurfaceProvider::CleanupResources()