diff --git a/Dockerfile b/Dockerfile
index f4fb46f..b182099 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM debian:12 AS builder
+FROM ubuntu:20.04 AS builder
 
 LABEL maintainer="Yury Muski <muski.yury@gmail.com>"
 
@@ -69,7 +69,7 @@ RUN curl -O https://nginx.org/download/nginx-$NGINX_VERSION.tar.gz && \
     make && \
     make install;
 
-FROM debian:12-slim
+FROM ubuntu:20.04
 
 RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get install -y libpcre3 libbrotli1
diff --git a/README.md b/README.md
index a904c94..26d5bf5 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,6 @@ docker run -it --rm --name certbot \
 
 `docker run --name nginx -d -p 80:80 -p 443:443/tcp -p 443:443/udp -v ${PWD}/temp/letsencrypt/:/opt/nginx/certs/ -v ${PWD}/nginx.conf:/etc/nginx/nginx.conf  ymuski/nginx-http3`
 
-`docker run --name nginx -d -p 80:80 -p 443:443/tcp -p 443:443/udp -v /etc/letsencrypt/:/opt/nginx/certs/ -v /opt/nginx/conf/example.nginx.conf:/etc/nginx/nginx.conf  ymuski/nginx-http3`
 
 ### Checking
 
diff --git a/example.nginx.conf b/example.nginx.conf
index 9ced9a4..e5749fd 100644
--- a/example.nginx.conf
+++ b/example.nginx.conf
@@ -51,7 +51,7 @@ http {
         }
 
         # Add Alt-Svc header to negotiate HTTP/3.
-        add_header alt-svc 'h3-27=":443"; ma=86400, h3-28=":443"; ma=86400, h3-29=":443"; ma=86400, h3=":443"; ma=86400';
+        add_header alt-svc 'h3=":443"; ma=86400';
 
         location / {
             root   html;