Index: generic/nsfStack.c
===================================================================
diff -u -N -rb44aabd0e7bafe2698c981f6d60b2d266e66ff3b -r7c9627dd582ea07050a95a6e0bb05cdf381fe592
--- generic/nsfStack.c	(.../nsfStack.c)	(revision b44aabd0e7bafe2698c981f6d60b2d266e66ff3b)
+++ generic/nsfStack.c	(.../nsfStack.c)	(revision 7c9627dd582ea07050a95a6e0bb05cdf381fe592)
@@ -1041,7 +1041,7 @@
   { int count = 0;
     NsfClasses *unstackedEntries = RUNTIME_STATE(interp)->cscList, *nextCscPtr = unstackedEntries;
 
-    while (nextCscPtr) {
+    while (nextCscPtr != NULL) {
       NsfCallStackContent *cscPtr = (NsfCallStackContent *)nextCscPtr->cl;
       CscListRemove(interp, cscPtr, &unstackedEntries);
       CscFinish(interp, cscPtr, TCL_OK, "unwind");