diff --git a/lib/Db/Restriction.php b/lib/Db/Restriction.php
index b014204..2614571 100644
--- a/lib/Db/Restriction.php
+++ b/lib/Db/Restriction.php
@@ -34,8 +34,8 @@ class Restriction extends Entity implements JsonSerializable {
 		$this->addType('allowRecording', 'boolean');
 	}
 
-	public function setGroupName(string $groupName) {
-		$this->groupName = $groupName;
+	public function setGroupName(?string $groupName) {
+		$this->groupName = $groupName ?? '';
 	}
 
 	public function jsonSerialize(): array {