diff --git a/build/entry.sh b/build/entry.sh
index 85e7c0f..ceda8f7 100755
--- a/build/entry.sh
+++ b/build/entry.sh
@@ -38,7 +38,7 @@ if is_enabled "$KILL_SWITCH"; then
 fi
 
 # Docker secret that contains the credentials for accessing the VPN.
-if [[ $AUTH_SECRET ]]; then
+if [[ ! -z "${AUTH_SECRET-}" ]]; then
     openvpn_args+=("--auth-user-pass" "/run/secrets/$AUTH_SECRET")
 fi