diff --git a/vulnz/src/docker/scripts/mirror.sh b/vulnz/src/docker/scripts/mirror.sh
index b13f250f..fb714aea 100755
--- a/vulnz/src/docker/scripts/mirror.sh
+++ b/vulnz/src/docker/scripts/mirror.sh
@@ -7,7 +7,7 @@ if [ -z $NVD_API_KEY ]; then
   DELAY_ARG="--delay=10000"
 fi
 
-if [ -z $DELAY ]; then
+if [ -n "${DELAY}" ]; then
   DELAY_ARG="--delay=$DELAY"
 fi