diff --git a/apps/files_external/lib/config.php b/apps/files_external/lib/config.php
index 4364307651..de42fe2f75 100755
--- a/apps/files_external/lib/config.php
+++ b/apps/files_external/lib/config.php
@@ -266,6 +266,11 @@ class OC_Mount_Config {
 										 $mountType,
 										 $applicable,
 										 $isPersonal = false) {
+		$mountPoint = OC\Files\Filesystem::normalizePath($mountPoint);
+		if ($mountPoint === '' || $mountPoint === '/') {
+			// can't mount at root
+			return false;
+		}
 		if ($isPersonal) {
 			// Verify that the mount point applies for the current user
 			// Prevent non-admin users from mounting local storage