diff --git a/etc/docker/environment/Dockerfile b/etc/docker/environment/Dockerfile
index f4e8a5d87..f57da44eb 100644
--- a/etc/docker/environment/Dockerfile
+++ b/etc/docker/environment/Dockerfile
@@ -1,8 +1,8 @@
 # Ubuntu image with tools required to build OpenThread
 FROM ubuntu:22.04
 
-ENV DEBIAN_FRONTEND noninteractive
-ENV LANG en_US.UTF-8
+ENV DEBIAN_FRONTEND=noninteractive
+ENV LANG=en_US.UTF-8
 
 # Resolves issue with installing libc-bin
 RUN rm /var/lib/dpkg/info/libc-bin.* \