diff --git a/panda/src/display/graphicsEngine.cxx b/panda/src/display/graphicsEngine.cxx
index d7e46110ba..beec7e15be 100644
--- a/panda/src/display/graphicsEngine.cxx
+++ b/panda/src/display/graphicsEngine.cxx
@@ -663,6 +663,7 @@ render_frame() {
       }
     }
   }
+  _windows.swap(new_windows);
 
   // Now it's time to do any drawing from the main frame--after all of
   // the App code has executed, but before we begin the next frame.