diff --git a/SMILEBASIC/graphic.d b/SMILEBASIC/graphic.d
index 89cab86..80b55f8 100644
--- a/SMILEBASIC/graphic.d
+++ b/SMILEBASIC/graphic.d
@@ -435,6 +435,7 @@ class Graphic
                 {
                     i.deleteGL;
                 }
+                oldGRP = null;
             }
             initGLGraphicPages();
         }