diff --git a/lib/fileproxy/quota.php b/lib/fileproxy/quota.php
index 0b2b584870..82eca1ce44 100644
--- a/lib/fileproxy/quota.php
+++ b/lib/fileproxy/quota.php
@@ -57,7 +57,7 @@ class OC_FileProxy_Quota extends OC_FileProxy{
 		$rootInfo=OC_FileCache::get('');
 		$sharedInfo=OC_FileCache::get('/Shared');
 		$usedSpace=isset($rootInfo['size'])?$rootInfo['size']:0;
-		$usedSpace=isset($sharedInfo['size'])?$rootInfo['size']-$sharedInfo['size']:$rootInfo['size'];
+		$usedSpace=isset($sharedInfo['size'])?$usedSpace-$sharedInfo['size']:$usedSpace;
 		$totalSpace=$this->getQuota();
 		if($totalSpace==0){
 			return 0;