diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index e9bd5a4b..c0ec26bb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -2,6 +2,9 @@ image: ruby:2.5
 stages:
   - build
 
+variables:
+  LANG: "C.UTF-8"
+
 before_script:
   - gem install bundler