diff --git a/docs/radar/README.md b/docs/radar/README.md
index deac2b18..5af02609 100644
--- a/docs/radar/README.md
+++ b/docs/radar/README.md
@@ -48,6 +48,7 @@ yum install tuxcare-radar
 APT-based distributions (Debian, Ubuntu etc):
 
 ```text
+apt-get update
 apt-get install tuxcare-radar
 ```