diff --git a/apps/files_sharing/lib/sharedstorage.php b/apps/files_sharing/lib/sharedstorage.php
index 59de2dfa4c474c56c5c9e333a7f51ab9e2126180..6760538f510bbfc5d4c4afcbb68eaec7e6321de5 100644
--- a/apps/files_sharing/lib/sharedstorage.php
+++ b/apps/files_sharing/lib/sharedstorage.php
@@ -23,12 +23,13 @@
 
 namespace OC\Files\Storage;
 use OC\Files\Filesystem;
+use OCA\Files_Sharing\ISharedStorage;
 use OCA\Files_Sharing\SharedMount;
 
 /**
  * Convert target path to source path and pass the function call to the correct storage provider
  */
-class Shared extends \OC\Files\Storage\Common {
+class Shared extends \OC\Files\Storage\Common implements ISharedStorage {
 
 	private $share;   // the shared resource
 	private $files = array();
diff --git a/lib/private/share/share.php b/lib/private/share/share.php
index 0a4d9a913e239080c45628abffe7c7d81b3d79c7..26108a937cec6aeaf8103bf0bba99f00b024647a 100644
--- a/lib/private/share/share.php
+++ b/lib/private/share/share.php
@@ -508,9 +508,9 @@ class Share extends \OC\Share\Constants {
 		if ($itemType === 'folder') {
 			$path = '/' . $uidOwner . '/files' . \OC\Files\Filesystem::getPath($itemSource) . '/';
 			$mountManager = \OC\Files\Filesystem::getMountManager();
-			$mounts = $mountManager->getAll();
-			foreach ($mounts as $mountPoint => $mount) {
-				if ($mount->getStorage() instanceof \OCA\Files_Sharing\ISharedStorage && strpos($mountPoint, $path) === 0) {
+			$mounts = $mountManager->findIn($path);
+			foreach ($mounts as $mount) {
+				if ($mount->getStorage()->instanceOfStorage('\OCA\Files_Sharing\ISharedStorage')) {
 					$message = 'Sharing "' . $itemSourceName . '" failed, because it contains files shared with you!';
 					\OC_Log::write('OCP\Share', $message, \OC_Log::ERROR);
 					throw new \Exception($message);