--- a/src/Plugin/facets/hierarchy/Taxonomy.php
+++ b/src/Plugin/facets/hierarchy/Taxonomy.php
@@ -185,7 +185,7 @@ class Taxonomy extends HierarchyPluginBase {
     return array_diff(
       array_merge(
         $childIds,
         $topLevelTerms,
-        (!$topLevelTerms && $parentSiblings) ? $this->getSiblingIds($ids, $parentIds) : []
+        (!$topLevelTerms && $parentSiblings) ? $this->getSiblingIds($parentIds) : []
       ),
       $ids
     );