diff --git a/gap/structure.gi b/gap/structure.gi
index 6e24126..5f888a8 100644
--- a/gap/structure.gi
+++ b/gap/structure.gi
@@ -465,7 +465,7 @@ end);
 
 OppHelper@ := function(Q, whichgens, cnstr)
   local fam, elts, opp;
-  elts := List(whichgen(Q), q -> OppositeObj(q));
+  elts := List(whichgens(Q), q -> OppositeObj(q));
   fam := CollectionsFamily(OppositeFamily(ElementsFamily(FamilyObj(Q))));
   opp := cnstr(fam, elts);
   if HasIsFinite(Q) then SetIsFinite(opp, IsFinite(Q)); fi;