diff --git a/lib/Activity/Listener.php b/lib/Activity/Listener.php
index 624f4f824..f4a294159 100644
--- a/lib/Activity/Listener.php
+++ b/lib/Activity/Listener.php
@@ -114,7 +114,7 @@ protected function generateNewSignNotificationActivity(
 				),
 				'signRequest' => [
 					'type' => 'sign-request',
-					'id' => $signRequest->getId(),
+					'id' => (string)$signRequest->getId(),
 					'name' => $actor->getDisplayName(),
 				],
 			]);
@@ -126,12 +126,12 @@ protected function generateNewSignNotificationActivity(
 	}
 
 	/**
-	 * @return array{type: 'file', id: int, name: string, path: string, link: string}
+	 * @return array{type: 'file', id: string, name: string, path: string, link: string}
 	 */
 	protected function getFileParameter(SignRequest $signRequest, FileEntity $libreSignFile): array {
 		return [
 			'type' => 'file',
-			'id' => $libreSignFile->getNodeId(),
+			'id' => (string)$libreSignFile->getNodeId(),
 			'name' => $libreSignFile->getName(),
 			'path' => $libreSignFile->getName(),
 			'link' => $this->url->linkToRouteAbsolute('libresign.page.sign', ['uuid' => $signRequest->getUuid()]),
diff --git a/lib/Listener/NotificationListener.php b/lib/Listener/NotificationListener.php
index 9f0340c5b..bf82f393c 100644
--- a/lib/Listener/NotificationListener.php
+++ b/lib/Listener/NotificationListener.php
@@ -93,7 +93,7 @@ private function sendSignNotification(
 			'file' => $this->getFileParameter($signRequest, $libreSignFile),
 			'signRequest' => [
 				'type' => 'sign-request',
-				'id' => $signRequest->getId(),
+				'id' => (string)$signRequest->getId(),
 				'name' => $actor->getDisplayName(),
 			],
 		]);
@@ -122,14 +122,12 @@ public function isNotificationDisabledAtActivity(IIdentifyMethod $identifyMethod
 	}
 
 	/**
-	 * @return (int|string)[]
-	 *
-	 * @psalm-return array{type: 'file', id: int, name: string, path: string, link: string}
+	 * @psalm-return array{type: 'file', id: string, name: string, path: string, link: string}
 	 */
 	protected function getFileParameter(SignRequest $signRequest, FileEntity $libreSignFile): array {
 		return [
 			'type' => 'file',
-			'id' => $libreSignFile->getNodeId(),
+			'id' => (string)$libreSignFile->getNodeId(),
 			'name' => $libreSignFile->getName(),
 			'path' => $libreSignFile->getName(),
 			'link' => $this->url->linkToRouteAbsolute('libresign.page.sign', ['uuid' => $signRequest->getUuid()]),