diff --git a/Dockerfile.prod b/Dockerfile.prod
index 9e364dd..5fa7241 100644
--- a/Dockerfile.prod
+++ b/Dockerfile.prod
@@ -68,4 +68,4 @@ RUN sudo cp -a /tmp/riju/* /home/docker/src/ && rm -rf /tmp/riju
 
 WORKDIR /home/docker/src
 RUN sudo deluser docker sudo
-RUN RIJU_PRIVILEGED=1 CONCURRENCY=1 TIMEOUT_FACTOR=5 yarn test
+RUN RIJU_PRIVILEGED=1 CONCURRENCY=1 TIMEOUT_FACTOR=5 LANG=C.UTF-8 LC_ALL=C.UTF-8 yarn test