diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 044e8297..a18951cc 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -36,6 +36,11 @@ before_script:
   - apt-get -q update
   # install dependencies for packages
   - apt-get -y -q install libxml2-dev libssl-dev libcurl4-openssl-dev zlib1g-dev pandoc r-base
+  # set R system language
+  - echo "LC_ALL=en_US.UTF-8" >> /etc/environment
+  - echo "en_US.UTF-8 UTF-8" >> /etc/locale.gen
+  - echo "LANG=en_US.UTF-8" > /etc/locale.conf
+  - locale-gen en_US.UTF-8
   # cache R packages
   - mkdir -p installed_deps
   - echo 'R_LIBS="installed_deps"' > .Renviron