Index: trunk/Mars/msimreflector/MSimRays.cc
===================================================================
--- trunk/Mars/msimreflector/MSimRays.cc	(revision 9910)
+++ trunk/Mars/msimreflector/MSimRays.cc	(revision 9922)
@@ -43,4 +43,5 @@
 #include "MSimRays.h"
 
+#include <TMath.h>       // root >=5.20
 #include <TRandom.h>
 #include <TRotation.h>