diff --git a/diffscan.c b/diffscan.c
index 8639134e..32252513 100644
--- a/diffscan.c
+++ b/diffscan.c
@@ -178,6 +178,7 @@ static int StartDiffScan(pDiffScan self, pScanData pScan,
   self->scaleMonitor = (int)ObVal(self->parArray,DIFFMONITOR);
   self->normalizationScale = -1;
   pScan->iCounts = 0;
+  pScan->iNP = 0;
   
   /*
     get variable
@@ -188,7 +189,8 @@ static int StartDiffScan(pDiffScan self, pScanData pScan,
     SCWrite(pCon,"ERROR: cannot access scan variable",eError);
     return 0;
   }
-  
+  InitScanVar(pVar);
+
   /*
     drive to start position
   */