--- a/CPP/7zip/Archive/7z/7zIn.cpp	Sun Nov 20 09:29:41 2016
+++ b/CPP/7zip/Archive/7z/7zIn.cpp	Sun Nov 20 09:31:22 2016
@@ -1097,7 +1097,8 @@ HRESULT CInArchive::ReadAndDecodePackedStreams(
       if (CrcCalc(data, unpackSize) != folders.FolderCRCs.Vals[i])
         ThrowIncorrect();
   }
-  HeadersSize += folders.PackPositions[folders.NumPackStreams];
+  if (folders.PackPositions)
+      HeadersSize += folders.PackPositions[folders.NumPackStreams];
   return S_OK;
 }
 
