diff --git a/src/atom_vec_ellipsoid.cpp b/src/atom_vec_ellipsoid.cpp
index 77b105762243902d904057a5403b4e8926784c91..929e10e09b821fa70a3b161100546a44901d4e8e 100755
--- a/src/atom_vec_ellipsoid.cpp
+++ b/src/atom_vec_ellipsoid.cpp
@@ -185,6 +185,7 @@ void AtomVecEllipsoid::clear_bonus()
 
 /* ----------------------------------------------------------------------
    set shape values in bonus data for particle I
+   oriented aligned with xyz axes
    this may create or delete entry in bonus data
 ------------------------------------------------------------------------- */