diff --git a/Dockerfile b/Dockerfile
index 7cd9aed46eb2f8919baf0792b4ed6723bddc4997..e1aa7ce0faf4ff950910f7be0a79c588c382f0dc 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,6 @@
 FROM python:3
-ENV version=
 
-RUN pip install black$(version)
+ARG version
+ENV version=${version}
+
+RUN pip install black${version}