diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4f897719..e850083e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## 1.1.1 under development
 
 - Enh #424: Refactor `Makefile` default command help logic (@samdark)
+- Enh #435: Set locale `C.UTF-8` in `Dockerfile` (@vjik)
 
 ## 1.1.0 December 20, 2025
 
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 3c4711d1..67445c32 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -19,6 +19,8 @@ RUN install-php-extensions \
     simplexml \
     pdo
 
+ENV LC_ALL=C.UTF-8
+
 #
 # Development
 #