*** OldPyString.java	Wed Aug 01 17:50:33 2001
--- PyString.java	Wed Aug 01 17:52:12 2001
***************
*** 240,245 ****
--- 240,248 ----
      }
  
      public PyString(String string) {
+         if (string == null) {
+             throw new IllegalArgumentException("Cannot create PyString from null!");
+         }
          this.string = string;
      }