diff --git a/README.md b/README.md
index b1a46f4..3eb1684 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,8 @@ REVIEWDOG_VERSION=v0.1.0
 ```Dockerfile
 # Dockerfile sample
 ENV REVIEWDOG_VERSION=0.1.0
-ENV REVIEWDOG_VERSION 0.1.0 # space is ok.
+# space is supported as well.
+ENV REVIEWDOG_VERSION 0.1.0
 ARG REVIEWDOG_VERSION=0.1.0
 ```