diff --git a/scripts/start-deployPurpur b/scripts/start-deployPurpur
index 162da6c1..b8c182d1 100755
--- a/scripts/start-deployPurpur
+++ b/scripts/start-deployPurpur
@@ -2,6 +2,8 @@
 set -euo pipefail
 IFS=$'\n\t'
 
+: "${PURPUR_DOWNLOAD_URL:=}"
+
 # shellcheck source=start-utils
 . "${SCRIPTS:-/}start-utils"
 isDebugging && set -x