diff --git a/Oittm-Smart-Plug.md b/Oittm-Smart-Plug.md
index 72f99477..11f76c93 100644
--- a/Oittm-Smart-Plug.md
+++ b/Oittm-Smart-Plug.md
@@ -16,6 +16,8 @@ Remove the small plastics caps on the back and unscrew the first two screws and
 
 ## PCB layout
 
+**_!!Make sure to flash with 3.3V and disconnect the power plug from the main outlet before!!_**
+
 ![](https://dustplanet.de/wp-content/uploads/2018/12/IMG_4920.jpeg)
 ![](https://dustplanet.de/wp-content/uploads/2018/12/IMG_8727.jpeg)