diff --git a/images/ruby/.devcontainer/Dockerfile b/images/ruby/.devcontainer/Dockerfile
index 0d4a68d..441da28 100644
--- a/images/ruby/.devcontainer/Dockerfile
+++ b/images/ruby/.devcontainer/Dockerfile
@@ -4,4 +4,7 @@ RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \
     # Remove imagemagick due to https://security-tracker.debian.org/tracker/CVE-2019-10131
     && apt-get purge -y imagemagick imagemagick-6-common
 
+ENV LANG=C.UTF-8 \
+    LC_ALL=C.UTF-8
+
 USER vscode