Index: generic/nsfShadow.c
===================================================================
diff -u -r77b8c1919a102d9309079071f070f2f5b48d50a5 -rcaba76f5ac2943f5a3dfd33550cb578132f40c80
--- generic/nsfShadow.c	(.../nsfShadow.c)	(revision 77b8c1919a102d9309079071f070f2f5b48d50a5)
+++ generic/nsfShadow.c	(.../nsfShadow.c)	(revision caba76f5ac2943f5a3dfd33550cb578132f40c80)
@@ -4,7 +4,7 @@
  *      API support for shadowing (overloading) and accessing C-implemented
  *      Tcl obj-commands.
  *  
- *  Copyright (C) 1999-2012 Gustaf Neumann
+ *  Copyright (C) 1999-2014 Gustaf Neumann
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -280,7 +280,7 @@
       level -= topLevel;
     }
 
-    while (++level <= 0 && varFramePtr) {
+    while (++level <= 0 && varFramePtr && framePtr) {
       framePtr = framePtr->nextPtr;
       varFramePtr = varFramePtr->callerPtr;
     }