diff --git a/Framework/Crystal/src/SaveIsawPeaks.cpp b/Framework/Crystal/src/SaveIsawPeaks.cpp
index 0ce31ff541f1316332af3d68da8c7ed0a77dc023..ebccb80a5f28b8d86f3863d2d911e51d5a979a85 100644
--- a/Framework/Crystal/src/SaveIsawPeaks.cpp
+++ b/Framework/Crystal/src/SaveIsawPeaks.cpp
@@ -267,7 +267,7 @@ void SaveIsawPeaks::exec() {
   runMap_t::iterator runMap_it;
   for (runMap_it = runMap.begin(); runMap_it != runMap.end(); ++runMap_it) {
     // Start of a new run
-    appendPeakNumb += maxPeakNumb;
+    if (maxPeakNumb > 0) appendPeakNumb += maxPeakNumb + 1;
     int run = runMap_it->first;
     bankMap_t &bankMap = runMap_it->second;