diff --git a/src/classes/PRunSingleHistoRRF.cpp b/src/classes/PRunSingleHistoRRF.cpp
index 55f7ce02..b09aee8b 100644
--- a/src/classes/PRunSingleHistoRRF.cpp
+++ b/src/classes/PRunSingleHistoRRF.cpp
@@ -65,6 +65,8 @@ PRunSingleHistoRRF::PRunSingleHistoRRF() : PRunBase()
   // the fit range can be changed in the command block, these variables need to be accessible
   fGoodBins[0] = -1;
   fGoodBins[1] = -1;
+  
+  fN0EstimateEndTime = 1.0; // end time in (us) over which N0 is estimated.
 }
 
 //--------------------------------------------------------------------------
@@ -112,6 +114,8 @@ PRunSingleHistoRRF::PRunSingleHistoRRF(PMsrHandler *msrInfo, PRunDataHandler *ra
   fGoodBins[0] = -1;
   fGoodBins[1] = -1;
 
+  fN0EstimateEndTime = 1.0; // end time in (us) over which N0 is estimated.
+ 
   if (!PrepareData()) {
     cerr << endl << ">> PRunSingleHistoRRF::PRunSingleHistoRRF(): **SEVERE ERROR**: Couldn't prepare data for fitting!";
     cerr << endl << ">> This is very bad :-(, will quit ...";
diff --git a/src/include/PRunSingleHistoRRF.h b/src/include/PRunSingleHistoRRF.h
index 63b063eb..b937611c 100644
--- a/src/include/PRunSingleHistoRRF.h
+++ b/src/include/PRunSingleHistoRRF.h
@@ -58,7 +58,7 @@ class PRunSingleHistoRRF : public PRunBase
     virtual Bool_t PrepareViewData(PRawRunData* runData, const UInt_t histoNo);
 
   private:
-    static const Double_t fN0EstimateEndTime = 1.0; ///< end time in (us) over which N0 is estimated. Should eventually be estimated automatically ...
+    Double_t fN0EstimateEndTime; ///< end time in (us) over which N0 is estimated.
 
     UInt_t fNoOfFitBins;    ///< number of bins to be fitted
     Double_t fBackground;   ///< needed if background range is given (units: 1/bin)