Index: /trunk/MagicSoft/Mars/mpedestal/MPedCalcPedRun.cc
===================================================================
--- /trunk/MagicSoft/Mars/mpedestal/MPedCalcPedRun.cc	(revision 4004)
+++ /trunk/MagicSoft/Mars/mpedestal/MPedCalcPedRun.cc	(revision 4005)
@@ -393,6 +393,9 @@
             << Form("%s%2i%s",": Will use ",diff," samples from the Low-Gain for the High-Gain extraction")
             << endl;
-      fWindowSizeHiGain -= diff;
-      fWindowSizeLoGain += diff;
+
+      if ((Int_t)fWindowSizeHiGain > diff)
+        fWindowSizeHiGain -= diff;
+      else
+        fWindowSizeLoGain += fWindowSizeHiGain;
     }