diff --git a/macros_W/opentree.cxx b/macros_W/opentree.cxx
index b8e68a5085d57acf6be6202056bf0b20f016c163..457986df9dc377c6200f70092a1a508c97ffca82 100644
--- a/macros_W/opentree.cxx
+++ b/macros_W/opentree.cxx
@@ -1,3 +1,5 @@
+#include "TTree.h"
+
 void opentree()
 {