diff --git a/docker/Dockerfile.ci_lint b/docker/Dockerfile.ci_lint
index 8c52ebb449c0..61856fff96f4 100644
--- a/docker/Dockerfile.ci_lint
+++ b/docker/Dockerfile.ci_lint
@@ -43,3 +43,7 @@ RUN bash /install/ubuntu1804_install_clang_format.sh
 
 COPY install/ubuntu_install_nodejs.sh /install/ubuntu_install_nodejs.sh
 RUN bash /install/ubuntu_install_nodejs.sh
+
+# To prevent `black` command line errors caused by ASCII encoding
+ENV LC_ALL=C.UTF-8
+ENV LANG=C.UTF-8