diff --git a/tox.ini b/tox.ini
index da0fd3bfa..e9a8d0852 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,8 @@ install_command = pip install -U -c{env:UPPER_CONSTRAINTS_FILE:https://git.opens
 setenv =
   VIRTUAL_ENV={envdir}
   OS_TEST_PATH=./ironic_python_agent/tests/unit
+  LANGUAGE=en_US
+  LC_ALL=en_US.utf-8
 deps = -r{toxinidir}/test-requirements.txt
 commands = ostestr {posargs}