diff --git a/ipv6-update.rsc b/ipv6-update.rsc
index 2838feb..7e1d34f 100644
--- a/ipv6-update.rsc
+++ b/ipv6-update.rsc
@@ -14,6 +14,9 @@
 
 :global LogPrintExit2;
 :global ParseKeyValueStore;
+:global ScriptLock;
+
+$ScriptLock $0;
 
 :if ([ :typeof $PdPrefix ] = "nothing") do={
   $LogPrintExit2 error $0 ("This script is supposed to run from ipv6 dhcp-client.") true;