diff --git a/lib/Service/FederatedUserService.php b/lib/Service/FederatedUserService.php
index 2be236b07..4394f138c 100644
--- a/lib/Service/FederatedUserService.php
+++ b/lib/Service/FederatedUserService.php
@@ -1202,7 +1202,7 @@ private function getCachedSingleCircle(FederatedUser $federatedUser): Circle {
 		$key = $this->generateCacheKey($federatedUser);
 		$cachedData = $this->cache->get($key);
 
-		if ($cachedData === null) {
+		if (!is_string($cachedData)) {
 			throw new SingleCircleNotFoundException();
 		}