diff --git a/siteupdate/python-teresco/siteupdate.py b/siteupdate/python-teresco/siteupdate.py
index 94c679b2..7c7ce56c 100755
--- a/siteupdate/python-teresco/siteupdate.py
+++ b/siteupdate/python-teresco/siteupdate.py
@@ -3208,11 +3208,13 @@ def run(self):
 
         for w in r.point_list:
             # duplicate labels
+            # first, check primary label
             lower_label = w.label.lower().strip("+*")
             if lower_label in all_route_labels:
                 datacheckerrors.append(DatacheckEntry(r,[lower_label],"DUPLICATE_LABEL"))
             else:
                 all_route_labels.add(lower_label)
+            # then check alt labels
             for label in w.alt_labels:
                 lower_label = label.lower().strip("+*")
                 if lower_label in all_route_labels: