diff --git a/tutorials/tree/cernbuild.C b/tutorials/tree/cernbuild.C
index ba516b6..793ecb5 100644
--- a/tutorials/tree/cernbuild.C
+++ b/tutorials/tree/cernbuild.C
@@ -2,6 +2,11 @@
 // see also a variant in staff.C
 // Author: Rene Brun
    
+#include "TFile.h"
+#include "TSystem.h"
+#include "TString.h"
+#include "TTree.h"
+
 TFile *cernbuild(Int_t get=0, Int_t print=1) {
 
    Int_t           Category;