diff --git a/src/acdhOeaw/arche/lib/ingest/SkosVocabulary.php b/src/acdhOeaw/arche/lib/ingest/SkosVocabulary.php
index bc530d9..b639e88 100644
--- a/src/acdhOeaw/arche/lib/ingest/SkosVocabulary.php
+++ b/src/acdhOeaw/arche/lib/ingest/SkosVocabulary.php
@@ -409,7 +409,7 @@ public function preprocess(): self {
         $this->assureTitles($entitiesCollections);
         $this->dropProperties($entitiesCollections);
         $this->assureLiterals($entitiesCollections);
-        $this->assureParents(array_diff($entitiesCollections. [$this->vocabularyUrl]));
+        $this->assureParents(array_diff($entitiesCollections, [$this->vocabularyUrl]));
         $this->dropNodes($entitiesCollections);
         parent::preprocess();