diff --git a/src/Classic/Algorithms/PartBunch.cpp b/src/Classic/Algorithms/PartBunch.cpp
index 43a320820092b53a958c0a2f3e796cce6871e207..e187eb17d2ebee817c1994bb751b8a0e4879de10 100644
--- a/src/Classic/Algorithms/PartBunch.cpp
+++ b/src/Classic/Algorithms/PartBunch.cpp
@@ -1921,6 +1921,8 @@ void PartBunch::calcMoments() {
     }
 
     /*
+      Issue #72 is touching on this
+
       In OPAL Cycl the particle with ID=0
       is a special particle, a kind of design particle.