diff --git a/apps/files_versions/lib/expiration.php b/apps/files_versions/lib/expiration.php
index 02885e823ca..d42c62f0ee3 100644
--- a/apps/files_versions/lib/expiration.php
+++ b/apps/files_versions/lib/expiration.php
@@ -112,6 +112,10 @@ class Expiration {
 		return $isOlderThanMax || $isMinReached;
 	}
 
+	/**
+	* Read versions_retention_obligation, validate it 
+	* and set private members accordingly
+	*/
 	private function parseRetentionObligation(){
 		$splitValues = explode(',', $this->retentionObligation);
 		if (!isset($splitValues[0])) {