Index: trunk/MagicSoft/Mars/msignal/MExtractor.cc
===================================================================
--- trunk/MagicSoft/Mars/msignal/MExtractor.cc	(revision 4190)
+++ trunk/MagicSoft/Mars/msignal/MExtractor.cc	(revision 4235)
@@ -181,4 +181,8 @@
   Int_t lastdesired   = (Int_t)(fLoGainLast);
   Int_t lastavailable = (Int_t)fRunHeader->GetNumSamplesLoGain()-1;
+
+  if (lastavailable < 0)
+    *fLog << warn << GetDescriptor() 
+          << ": WARNING: Number of available Low-Gain Slices is smaller than or equal zero!" << endl;
   
   if (lastdesired > lastavailable)
@@ -197,4 +201,11 @@
   lastavailable = (Int_t)fRunHeader->GetNumSamplesHiGain()-1;
   
+  if (lastavailable < 0)
+    {
+      *fLog << err << GetDescriptor() 
+            << ": ERROR: Number of available High-Gain Slices is smaller than or equal zero!" << endl;
+      return kFALSE;
+    }
+
   if (lastdesired > lastavailable)
     {