diff --git a/check-lte-firmware-upgrade.rsc b/check-lte-firmware-upgrade.rsc
index c5b6cb56..71ff43e1 100644
--- a/check-lte-firmware-upgrade.rsc
+++ b/check-lte-firmware-upgrade.rsc
@@ -9,7 +9,8 @@
 # https://rsc.eworm.de/doc/check-lte-firmware-upgrade.md
 
 :global GlobalFunctionsReady;
-:while ($GlobalFunctionsReady != true) do={ :delay 500ms; }
+:onerror e { :retry { :if ($GlobalFunctionsReady != true) \
+  do={ :error "Global functions not ready."; }; } delay=500ms max=20; } do={ :log error $e; };
 
 :local ExitOK false;
 :do {