diff --git a/qgepqwat2ili/utils/qgep_export_utils.py b/qgepqwat2ili/utils/qgep_export_utils.py
index 80ae9fe7..d6b8ecda 100644
--- a/qgepqwat2ili/utils/qgep_export_utils.py
+++ b/qgepqwat2ili/utils/qgep_export_utils.py
@@ -1067,7 +1067,7 @@ def export_cover(self):
         # )
         # filtering only on wastewater_structures that are in subset_wws_ids
         if self.filtered:
-            query = query.join(self.qgep_model.wastewater_structure).filter(
+            query = query.join(self.qgep_model.wastewater_structure, cover.fk_wastewater_structure = wastewater_structure.obj_id).filter(
                 self.qgep_model.wastewater_structure.obj_id.in_(self.subset_wws_ids)
             )
         # add sql statement to logger
@@ -1116,7 +1116,7 @@ def export_cover(self):
     def export_cover_ws_off_sia405abwasser(self):
         query = self.qgep_session.query(self.qgep_model.cover)
         # if ws_off_sia405abwasser always filter out with subset_wws_ids
-        query = query.join(self.qgep_model.wastewater_structure).filter(
+        query = query.join(self.qgep_model.wastewater_structure, cover.fk_wastewater_structure = wastewater_structure.obj_id).filter(
             self.qgep_model.wastewater_structure.obj_id.in_(self.subset_wws_ids)
         )
         # add sql statement to logger