diff --git a/apps/files_sharing/lib/external/storage.php b/apps/files_sharing/lib/external/storage.php
index 91beccf74916a364bd3c562a9165005617733be5..0238f5ad4afa05ba4e9d76b5da107eb84f3e25fe 100644
--- a/apps/files_sharing/lib/external/storage.php
+++ b/apps/files_sharing/lib/external/storage.php
@@ -199,6 +199,11 @@ class Storage extends DAV implements ISharedStorage {
 			$this->manager->removeShare($this->mountPoint);
 			$this->manager->getMountManager()->removeMount($this->mountPoint);
 			throw new StorageInvalidException();
+		} catch (\GuzzleHttp\Exception\RequestException $e) {
+			if ($e->getCode() === 503) {
+				throw new StorageNotAvailableException();
+			}
+			throw $e;
 		} catch (\Exception $e) {
 			throw $e;
 		}