diff --git a/api/src/CalDAV/JsBase.php b/api/src/CalDAV/JsBase.php
index 9a3d7d1cb0..76b406735f 100644
--- a/api/src/CalDAV/JsBase.php
+++ b/api/src/CalDAV/JsBase.php
@@ -265,6 +265,7 @@ class JsBase
 	 * Parse categories object
 	 *
 	 * @param array $categories category-name => true pairs
+	 * @param bool $multiple
 	 * @return ?string comma-separated cat_id's
 	 * @todo make that generic, so JsContact & JSCalendar have not to overwrite it
 	 */
diff --git a/api/src/CalDAV/JsCalendar.php b/api/src/CalDAV/JsCalendar.php
index 06d2d31a48..74cb2115e1 100644
--- a/api/src/CalDAV/JsCalendar.php
+++ b/api/src/CalDAV/JsCalendar.php
@@ -205,9 +205,10 @@ class JsCalendar extends JsBase
 	 * Parse categories object
 	 *
 	 * @param array $categories category-name => true pairs
+	 * @param bool $multiple
 	 * @return ?string comma-separated cat_id's
 	 */
-	protected static function parseCategories(array $categories)
+	protected static function parseCategories(array $categories, bool $multiple=true)
 	{
 		static $bo=null;
 		$cat_ids = [];
diff --git a/api/src/Contacts/JsContact.php b/api/src/Contacts/JsContact.php
index 5b2329fab4..c5b8fbd304 100644
--- a/api/src/Contacts/JsContact.php
+++ b/api/src/Contacts/JsContact.php
@@ -351,9 +351,10 @@ class JsContact extends Api\CalDAV\JsBase
 	 * Parse categories object
 	 *
 	 * @param array $categories category-name => true pairs
+	 * @param bool $multiple
 	 * @return ?string comma-separated cat_id's
 	 */
-	protected static function parseCategories(array $categories)
+	protected static function parseCategories(array $categories, bool $multiple=true)
 	{
 		static $bo=null;
 		$cat_ids = [];