diff --git a/lib/private/FilesMetadata/FilesMetadataManager.php b/lib/private/FilesMetadata/FilesMetadataManager.php
index b6077f1f27125..0ac6963ad1f1e 100644
--- a/lib/private/FilesMetadata/FilesMetadataManager.php
+++ b/lib/private/FilesMetadata/FilesMetadataManager.php
@@ -164,6 +164,10 @@ public function saveMetadata(IFilesMetadata $filesMetadata): void {
 		}
 
 		$json = json_encode($filesMetadata->jsonSerialize());
+		if (!$json) {
+			$this->logger->error('Failed to json encode file metadata for ' . $filesMetadata->getFileId(), ['metadata' => $filesMetadata->jsonSerialize()]);
+			return;
+		}
 		if (strlen($json) > self::JSON_MAXSIZE) {
 			$this->logger->debug('huge metadata content detected: ' . $json);
 			throw new FilesMetadataException('json cannot exceed ' . self::JSON_MAXSIZE . ' characters long; fileId: ' . $filesMetadata->getFileId() . '; size: ' . strlen($json));