--- formula.c.orig	Thu Nov  4 15:01:23 1999
+++ formula.c	Thu Nov  4 15:01:27 1999
@@ -642,7 +642,7 @@
   new_record = malloc (sizeof (stack_record));
   test (new_record != NULL, 10);
   if (data == NULL)
-    new_record->data == NULL;
+    new_record->data = NULL;
   else
   {
     new_record->data = data;