diff --git a/capsman-rolling-upgrade b/capsman-rolling-upgrade
index 7723f93..7e172cc 100644
--- a/capsman-rolling-upgrade
+++ b/capsman-rolling-upgrade
@@ -5,6 +5,10 @@
 #
 # upgrade CAPs one after another
 
+:global ScriptLock;
+
+$ScriptLock "capsman-rolling-upgrade";
+
 :local InstalledVersion [ / system package update get installed-version ];
 
 :local RemoteCapCount [ /caps-man remote-cap print count-only ];