diff --git a/apps/files_external/lib/webdav.php b/apps/files_external/lib/webdav.php
index 0f8034e57d..f6f4cb16e8 100644
--- a/apps/files_external/lib/webdav.php
+++ b/apps/files_external/lib/webdav.php
@@ -224,7 +224,7 @@ class DAV extends \OC\Files\Storage\Common{
 			if (isset($response['{DAV:}quota-available-bytes'])) {
 				return (int)$response['{DAV:}quota-available-bytes'];
 			} else {
-				return 0;
+				return \OC\Files\SPACE_UNKNOWN;
 			}
 		} catch(\Exception $e) {
 			return \OC\Files\SPACE_UNKNOWN;