diff --git a/LArCalorimeter/LArG4/LArG4Code/src/LArG4BirksLaw.cc b/LArCalorimeter/LArG4/LArG4Code/src/LArG4BirksLaw.cc
index 248ccc38331a37c52deca8c0ce5d4a1562380d6e..5060270478f19d8285fb9d06d55f3dc0ebe8c147 100644
--- a/LArCalorimeter/LArG4/LArG4Code/src/LArG4BirksLaw.cc
+++ b/LArCalorimeter/LArG4/LArG4Code/src/LArG4BirksLaw.cc
@@ -18,6 +18,7 @@ double LArG4BirksLaw::operator () (double dE, double dX, double EField) const {
   double dEdX = dE/dX;
 
   const double kOverField = m_BirksLawK/EField;
+  // NB For a MIP in LAr 1.51 == dEdX/m_LArDensity, so dEcorr1==dE
   double dEcorr1 = dE * (1 + kOverField*1.51) / (1 + kOverField*dEdX/m_LArDensity);  // original corrections
 
   if (dEdX > 12000.0) dEdX = 12000.0;   // The experimental data is available only until dE/dX ~ 12000 MeV/cm