diff --git a/Dockerfile b/Dockerfile
index 6f7490e..fea246c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,7 +4,7 @@ FROM nginxinc/nginx-unprivileged:alpine-slim
 ENV REDIRECT_TARGET="https://example.com" \
     REDIRECT_CODE="301" \
     LISTEN_PORT="8080" \
-    NGINX_ENVSUBST_FILTER="REDIRECT_TARGET REDIRECT_CODE LISTEN_PORT"
+    NGINX_ENVSUBST_FILTER="LISTEN_PORT|REDIRECT_CODE|REDIRECT_TARGET"
 
 # Copy template for automatic envsubst rendering on startup
 COPY templates/default.conf.template /etc/nginx/templates/default.conf.template