diff --git a/Dockerfile.dev b/Dockerfile.dev
index c7e3ef4..17038d8 100644
--- a/Dockerfile.dev
+++ b/Dockerfile.dev
@@ -1,5 +1,7 @@
 FROM node:15.14.0-alpine3.12
 
+ENV REVEAL_JS_VERSION=4.1.0
+
 RUN set -ex \
   && apk add --no-cache \
     g++ \
@@ -9,10 +11,10 @@ RUN set -ex \
     wget
 
 RUN set -ex \
-  && wget https://github.com/hakimel/reveal.js/archive/refs/tags/4.1.0.zip \
-  && unzip 4.1.0.zip
+  && wget https://github.com/hakimel/reveal.js/archive/refs/tags/${REVEAL_JS_VERSION}.zip \
+  && unzip ${REVEAL_JS_VERSION}.zip
 
-WORKDIR /reveal.js-4.1.0
+WORKDIR "/reveal.js-${REVEAL_JS_VERSION}"
 
 RUN set -ex \
   && npm i