diff --git a/apps/dav/lib/CardDAV/Activity/Provider/Base.php b/apps/dav/lib/CardDAV/Activity/Provider/Base.php
index 0a1b55efb080d..efc7827c22051 100644
--- a/apps/dav/lib/CardDAV/Activity/Provider/Base.php
+++ b/apps/dav/lib/CardDAV/Activity/Provider/Base.php
@@ -55,14 +55,14 @@ protected function generateAddressbookParameter(array $data, IL10N $l): array {
 			$data['name'] === CardDavBackend::PERSONAL_ADDRESSBOOK_NAME) {
 			return [
 				'type' => 'addressbook',
-				'id' => $data['id'],
+				'id' => (string)$data['id'],
 				'name' => $l->t('Personal'),
 			];
 		}
 
 		return [
 			'type' => 'addressbook',
-			'id' => $data['id'],
+			'id' => (string)$data['id'],
 			'name' => $data['name'],
 		];
 	}
diff --git a/apps/systemtags/lib/Activity/Provider.php b/apps/systemtags/lib/Activity/Provider.php
index e555fc56a5051..ab8e326d8d989 100644
--- a/apps/systemtags/lib/Activity/Provider.php
+++ b/apps/systemtags/lib/Activity/Provider.php
@@ -285,7 +285,7 @@ protected function getParameters(IEvent $event) {
 	protected function getFileParameter($id, $path) {
 		return [
 			'type' => 'file',
-			'id' => $id,
+			'id' => (string)$id,
 			'name' => basename($path),
 			'path' => trim($path, '/'),
 		];
@@ -296,7 +296,7 @@ protected function getSystemTagParameter($parameter) {
 		if ($tagData === null) {
 			[$name, $status] = explode('|||', substr($parameter, 3, -3));
 			$tagData = [
-				'id' => 0,// No way to recover the ID
+				'id' => '0',// No way to recover the ID
 				'name' => $name,
 				'assignable' => $status === 'assignable',
 				'visible' => $status !== 'invisible',
@@ -305,7 +305,7 @@ protected function getSystemTagParameter($parameter) {
 
 		return [
 			'type' => 'systemtag',
-			'id' => (int) $tagData['id'],
+			'id' => (string)$tagData['id'],
 			'name' => $tagData['name'],
 			'assignable' => $tagData['assignable'] ? '1' : '0',
 			'visibility' => $tagData['visible'] ? '1' : '0',