diff -dur -x '*~' celestia-1.6.1.orig/src/celengine/frametree.h celestia-1.6.1/src/celengine/frametree.h
--- celestia-1.6.1.orig/src/celengine/frametree.h	2011-06-05 18:11:09.000000000 +0200
+++ celestia-1.6.1/src/celengine/frametree.h	2015-07-10 19:35:49.882049018 +0200
@@ -49,7 +49,7 @@
 
     bool isRoot() const
     {
-        return bodyParent == NULL;
+        return bodyParent == 0;
     }
 
     bool updateRequired() const