diff --git a/lib/private/AppFramework/OCS/BaseResponse.php b/lib/private/AppFramework/OCS/BaseResponse.php
index d367574a179bb..3b0a28fe89cdf 100644
--- a/lib/private/AppFramework/OCS/BaseResponse.php
+++ b/lib/private/AppFramework/OCS/BaseResponse.php
@@ -143,8 +143,10 @@ protected function toXML(array $array, \XMLWriter $writer): void {
 				$writer->startElement($k);
 				$this->toXML($v->jsonSerialize(), $writer);
 				$writer->endElement();
+			} elseif ($v === null) {
+				$writer->writeElement($k);
 			} else {
-				$writer->writeElement($k, $v);
+				$writer->writeElement($k, (string)$v);
 			}
 		}
 	}