--- a/src/pt-arg-list.h
+++ b/src/pt-arg-list.h
@@ -45,9 +45,13 @@
 {
 public:
 
-  tree_argument_list (void) { }
+  typedef tree_expression* element_type;
 
-  tree_argument_list (tree_expression *t) { append (t); }
+  tree_argument_list (void)
+    : list_includes_magic_end (false) { }
+
+  tree_argument_list (tree_expression *t)
+    : list_includes_magic_end (false) { append (t); }
 
   ~tree_argument_list (void);
 
@@ -59,6 +63,8 @@
       return retval;
     }
 
+  void append (const element_type& s);
+
   int nargout_count (void) const;
 
   bool all_elements_are_constant (void) const;
@@ -71,6 +77,8 @@
 
 private:
 
+  bool list_includes_magic_end;
+
   // No copying!
 
   tree_argument_list (const tree_argument_list&);