diff --git a/src/fix_ave_atom.cpp b/src/fix_ave_atom.cpp
index d69edf87a2..b604977f7e 100644
--- a/src/fix_ave_atom.cpp
+++ b/src/fix_ave_atom.cpp
@@ -350,6 +350,7 @@ void FixAveAtom::end_of_step()
       }
 
     // evaluate atom-style variable
+    // final argument = 1 sums result to array
 
     } else if (which[m] == VARIABLE && array)
       input->variable->compute_atom(n,igroup,&array[0][m],nvalues,1);