diff --git a/Source/BinaryTreeNode.m b/Source/BinaryTreeNode.m
index c4fdabf09..983d7aa08 100644
--- a/Source/BinaryTreeNode.m
+++ b/Source/BinaryTreeNode.m
@@ -1,5 +1,5 @@
 /* Implementation for Objective-C BinaryTreeNode object
-   Copyright (C) 1993,1994, 1995 Free Software Foundation, Inc.
+   Copyright (C) 1993,1994, 1995, 1996 Free Software Foundation, Inc.
 
    Written by:  R. Andrew McCallum <mccallum@gnu.ai.mit.edu>
    Date: May 1993
@@ -22,6 +22,7 @@
 */ 
 
 #include <objects/BinaryTreeNode.h>
+#include <objects/NSString.h>
 
 @implementation BinaryTreeNode