diff --git a/Dockerfile b/Dockerfile
index 7a2efbbc..2c216e96 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,7 @@
 FROM ruby:2.5.1
 
+ENV LANG=C.UTF-8
+
 WORKDIR /devdocs
 
 RUN apt-get update && \