diff --git a/panda/src/wgldisplay/config_wgldisplay.cxx b/panda/src/wgldisplay/config_wgldisplay.cxx
index 9fd053c79b..bb36621146 100644
--- a/panda/src/wgldisplay/config_wgldisplay.cxx
+++ b/panda/src/wgldisplay/config_wgldisplay.cxx
@@ -55,3 +55,6 @@ init_libwgldisplay() {
 
 int gl_force_pixfmt = config_wgldisplay.GetInt("gl-force-pixfmt", 0);
 
+// Set this true to force all GL windows to fail to open correctly.
+bool gl_force_invalid = config_wgldisplay.GetBool("gl-force-invalid", false);
+
diff --git a/panda/src/wgldisplay/config_wgldisplay.h b/panda/src/wgldisplay/config_wgldisplay.h
index 34908c35bb..5e7ad9e90d 100644
--- a/panda/src/wgldisplay/config_wgldisplay.h
+++ b/panda/src/wgldisplay/config_wgldisplay.h
@@ -27,5 +27,6 @@ NotifyCategoryDecl(wgldisplay, EXPCL_PANDAGL, EXPTP_PANDAGL);
 extern EXPCL_PANDAGL void init_libwgldisplay();
 
 extern int gl_force_pixfmt;
+extern bool gl_force_invalid;
 
 #endif
diff --git a/panda/src/wgldisplay/wglGraphicsWindow.cxx b/panda/src/wgldisplay/wglGraphicsWindow.cxx
index c04c584f82..61b9e09e2e 100644
--- a/panda/src/wgldisplay/wglGraphicsWindow.cxx
+++ b/panda/src/wgldisplay/wglGraphicsWindow.cxx
@@ -180,12 +180,14 @@ open_window() {
   // Initializes _colormap
   setup_colormap();
 
-  /*
-  wgldisplay_cat.error()
-    << "Artificially failing window.\n";
-  close_window();
-  return false;
-  */
+#ifndef NDEBUG
+  if (gl_force_invalid) {
+    wgldisplay_cat.error()
+      << "Artificially failing window.\n";
+    close_window();
+    return false;
+  }
+#endif  // NDEBUG
 
   return true;
 }