Index: generic/nsf.c
===================================================================
diff -u -r6eee126915e363e7bdc5d2e43a1157b791247e30 -rea57317ca22ddd156bfe6ffcba5361caaa19a970
--- generic/nsf.c	(.../nsf.c)	(revision 6eee126915e363e7bdc5d2e43a1157b791247e30)
+++ generic/nsf.c	(.../nsf.c)	(revision ea57317ca22ddd156bfe6ffcba5361caaa19a970)
@@ -5737,7 +5737,7 @@
   Tcl_Obj **ov; int oc;
   NsfTclObjList *last = NULL;
 
-  if (Tcl_ListObjGetElements(interp, aObj, &oc, &ov) == TCL_OK) {
+  if (aObj && Tcl_ListObjGetElements(interp, aObj, &oc, &ov) == TCL_OK) {
     if (oc > 0) {
       int i;
       for (i = oc - 1; i >= 0; i--) {