diff --git a/src/configure-balena-host-envvars.sh b/src/configure-balena-host-envvars.sh
index d3b000e4..dfe764ab 100755
--- a/src/configure-balena-host-envvars.sh
+++ b/src/configure-balena-host-envvars.sh
@@ -36,17 +36,17 @@ HOST_ENVVARS[BALENA_SENTRY_URL_HOST]=sentry
 HOST_ENVVARS[BALENA_MONITOR_HOST]=monitor
 
 # Go through the lists and fill in any missing envvars
-#for index in $(seq 1 ${#HOST_ENVVARS[*]}); do
 for VARNAME in "${!HOST_ENVVARS[@]}"; do
-    VARVALUE="${HOST_ENVVARS[$VARNAME]}"
-    if [[ ! -z "$VARVALUE" ]]; then
+    VARVALUE=${!VARNAME}
+    if [[ -z "$VARVALUE" ]]; then
+        PREFIX="${HOST_ENVVARS[$VARNAME]}"
         # Only use BALENA_DEVICE_UUID if it actually exists, else just use the
         # full passed in TLD
         DEVICE=""
         if [[ ! -z "$BALENA_DEVICE_UUID" ]]; then
             DEVICE="$BALENA_DEVICE_UUID."
         fi
-        SUBDOMAIN="$VARVALUE.$DEVICE$BALENA_TLD"
+        SUBDOMAIN="$PREFIX.$DEVICE$BALENA_TLD"
 
         # Several vars require special formatting
         if [ "$VARNAME" == "BALENA_TOKEN_AUTH_REALM" ]; then