diff --git a/apps/contactsinteraction/lib/AddressBook.php b/apps/contactsinteraction/lib/AddressBook.php
index 3e581c9302..55819380b9 100644
--- a/apps/contactsinteraction/lib/AddressBook.php
+++ b/apps/contactsinteraction/lib/AddressBook.php
@@ -34,7 +34,6 @@ use OCA\DAV\DAV\Sharing\Plugin;
 use OCP\AppFramework\Db\DoesNotExistException;
 use OCP\IL10N;
 use Sabre\DAV\Exception\NotFound;
-use Sabre\DAV\Exception\NotImplemented;
 use Sabre\DAV\PropPatch;
 use Sabre\DAVACL\ACLTrait;
 use Sabre\DAVACL\IACL;
diff --git a/apps/dav/lib/CardDAV/Integration/ExternalAddressBook.php b/apps/dav/lib/CardDAV/Integration/ExternalAddressBook.php
index 0bd01184eb..ac52a44630 100644
--- a/apps/dav/lib/CardDAV/Integration/ExternalAddressBook.php
+++ b/apps/dav/lib/CardDAV/Integration/ExternalAddressBook.php
@@ -34,7 +34,7 @@ use Sabre\DAV;
 abstract class ExternalAddressBook implements IAddressBook, DAV\IProperties {
 
 	/** @var string */
-	private const PREFIX = 'app-generated';
+	private const PREFIX = 'z-app-generated';
 
 	/**
 	 * @var string