diff --git a/NPLib/CATS/TCATSPhysics.cxx b/NPLib/CATS/TCATSPhysics.cxx
index a7337dd0ba2afb204d1f4772cd1ad14d534c0fec..8cf31ae18c3c307edf9836e88ed50da28e5a9d48 100644
--- a/NPLib/CATS/TCATSPhysics.cxx
+++ b/NPLib/CATS/TCATSPhysics.cxx
@@ -180,7 +180,7 @@ void TCATSPhysics::BuildPhysicalEvent(){
   double CalculatedStripX = 0, CalculatedStripY = 0;
   double posX = 0 , posY = 0;
 
-  for(ff = 1 ; ff < NumberOfCATSHit ; ff++ ){       
+  for(ff = 0 ; ff < NumberOfCATSHit ; ff++ ){       
     CalculatedStripX = AnalyseX(ff);         
     CalculatedStripY = AnalyseY(ff);