diff --git a/Makefile b/Makefile
index d9fdb80..5edb3d0 100644
--- a/Makefile
+++ b/Makefile
@@ -11,15 +11,15 @@ TAG?=latest
 default: nginx ppm standalone
 
 nginx:
-	docker build -t phppm/nginx:${TAG} -f build/Dockerfile-nginx build/ --build-arg version=${VERSION} --build-arg http_version=${HTTP_VERSION}
+	docker build -t phppm/nginx:${TAG} -f build/Dockerfile-nginx build/ --build-arg version="${VERSION}" --build-arg http_version="${HTTP_VERSION}"
 	docker tag phppm/nginx:${TAG} phppm/nginx:latest
 
 ppm:
-	docker build -t phppm/ppm:${TAG} -f build/Dockerfile-ppm build/ --build-arg version=${VERSION} --build-arg http_version=${HTTP_VERSION}
+	docker build -t phppm/ppm:${TAG} -f build/Dockerfile-ppm build/ --build-arg version="${VERSION}" --build-arg http_version="${HTTP_VERSION}"
 	docker tag phppm/ppm:${TAG} phppm/ppm:latest
 
 standalone:
-	docker build -t phppm/standalone:${TAG} -f build/Dockerfile-standalone build/ --build-arg version=${VERSION} --build-arg http_version=${HTTP_VERSION}
+	docker build -t phppm/standalone:${TAG} -f build/Dockerfile-standalone build/ --build-arg version="${VERSION}" --build-arg http_version="${HTTP_VERSION}"
 	docker tag phppm/standalone:${TAG} phppm/standalone:latest
 
 push-all:
diff --git a/README.md b/README.md
index e84fbe7..89a0666 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ You can use [PHP-PM](https://github.com/php-pm/php-pm) using Docker. We provide
 
 ### Examples
 
-```
+```sh
 # change into your project folder first
 cd your/symfony-project/
 
@@ -39,7 +39,7 @@ $ docker run -v `pwd`:/var/www -p 80:80 phppm/nginx --workers=16
 
 Docker compose
 
-```
+```docker
 version: "3.1"
 
 services:
@@ -57,7 +57,7 @@ services:
 You should configure PPM via the ppm.json in the root directory, which is within the container mounted to 
 `/var/www/`. Alternatively, you can overwrite each option using the regular cli arguments.
 
-```
+```sh
 # change the ppm.json within current directory
 docker run -v `pwd`:/var/www phppm/ppm config --help
 
@@ -72,7 +72,7 @@ docker run -v `pwd`:/var/www -p 80:80 phppm/nginx --c prod-ppm.json
 If your applications requires additional php modules or other tools and libraries in your container, you
 can use our image as base. We use lightweight Alpine Linux.
 
-```
+```docker
 # Dockerfile
 FROM phppm/nginx:1.0
 
@@ -82,7 +82,7 @@ RUN apk --no-cache add ca-certificates wget
 # whatever you need 
 ```
 
-```
+```sh
 docker build vendor/my-image -f Dockerfile .
 # now use vendor/my-image instead of `phppm/nginx`
 ```
diff --git a/build/Dockerfile-nginx b/build/Dockerfile-nginx
index d3d3f6b..eadf4ea 100644
--- a/build/Dockerfile-nginx
+++ b/build/Dockerfile-nginx
@@ -2,7 +2,7 @@ FROM composer:1.9 as composer
 
 ARG version=dev-master
 ARG http_version=dev-master
-RUN mkdir /ppm && cd /ppm && composer require php-pm/php-pm:${version} && composer require php-pm/httpkernel-adapter:${http_version}
+RUN mkdir /ppm && cd /ppm && composer require php-pm/php-pm:"${version}" php-pm/httpkernel-adapter:"${http_version}"
 
 FROM alpine:3.11
 
diff --git a/build/Dockerfile-ppm b/build/Dockerfile-ppm
index b7715bf..1560ffe 100644
--- a/build/Dockerfile-ppm
+++ b/build/Dockerfile-ppm
@@ -2,7 +2,7 @@ FROM composer:1.9 as composer
 
 ARG version=dev-master
 ARG http_version=dev-master
-RUN mkdir /ppm && cd /ppm && composer require php-pm/php-pm:${version} && composer require php-pm/httpkernel-adapter:${http_version}
+RUN mkdir /ppm && cd /ppm && composer require php-pm/php-pm:"${version}" php-pm/httpkernel-adapter:"${http_version}"
 
 FROM alpine:3.11
 
diff --git a/build/Dockerfile-standalone b/build/Dockerfile-standalone
index fd28cec..b30c1e1 100644
--- a/build/Dockerfile-standalone
+++ b/build/Dockerfile-standalone
@@ -2,7 +2,7 @@ FROM composer:1.9 as composer
 
 ARG version=dev-master
 ARG http_version=dev-master
-RUN mkdir /ppm && cd /ppm && composer require php-pm/php-pm:${version} && composer require php-pm/httpkernel-adapter:${http_version}
+RUN mkdir /ppm && cd /ppm && composer require php-pm/php-pm:"${version}" php-pm/httpkernel-adapter:"${http_version}"
 
 FROM alpine:3.11