diff --git a/src/HybridNew.cc b/src/HybridNew.cc
index a0f36097023..63f6236f413 100644
--- a/src/HybridNew.cc
+++ b/src/HybridNew.cc
@@ -15,6 +15,7 @@
 #include <TGraphErrors.h>
 #include <TStopwatch.h>
 #include <TRandom3.h>
+#include <TTree.h>
 #include "RooRealVar.h"
 #include "RooArgSet.h"
 #include "RooAbsPdf.h"