diff --git a/README.md b/README.md
index 377335e..46bc0dc 100644
--- a/README.md
+++ b/README.md
@@ -131,6 +131,9 @@ PCBA production are recommended:
        If anything looks suspicious, ask also for X-ray imaging.
     6. Pay for the assembly and shipping.
 
+Ask manufacturer do they have qualified person able to follow instructions 
+for [ULX3S self-test](https://github.com/emard/ulx3s-bin).
+
 # Todo
 
 Test the prototype.