diff --git a/README.md b/README.md
index 87c2bca..b39d6c5 100644
--- a/README.md
+++ b/README.md
@@ -169,6 +169,8 @@ Here is an example CSS config which hides the local login and makes space for a
 
 ## Using [`previewgenerator`](https://github.com/nextcloud/previewgenerator) app
 
+> Beware, this appp has been known to not work...
+
 After you install, enable etc. then you need to run the generation (**warning**: it can take a long time!):
 
 ```