diff --git a/gap/structure.gi b/gap/structure.gi
index f033c3d..43671aa 100644
--- a/gap/structure.gi
+++ b/gap/structure.gi
@@ -529,6 +529,7 @@ RoughJoinOfFilters@ := function(list, first)
   for item in list{[2..Length(list)]} do
     IntersectSet(jof, FiltersOfObj@(item));
   od;
+  return jof;
 end;
 
 InstallOtherMethod(DirectProductOp, "for a list and non-quasigroup magma",