diff --git a/configure b/configure
index cd644158..ae073e77 100755
--- a/configure
+++ b/configure
@@ -1,5 +1,5 @@
 #!/bin/sh
-# $Id: configure,v 1.37 2009-09-16 12:36:27 nicm Exp $
+# $Id: configure,v 1.38 2009-09-20 17:51:54 nicm Exp $
 
 TMUX_PLATFORM=${TMUX_PLATFORM:-`uname -s`}
 
@@ -212,6 +212,7 @@ EOF
 #define HAVE_STRLCPY
 #define HAVE_STRTONUM
 #define HAVE_STRSEP
+#define HAVE_TREE_H
 #define HAVE_U_INT
 EOF
 	cat <<EOF >>$CONFIG_MK