diff --git a/tox.ini b/tox.ini
index 70265ee..35042e5 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,17 +1,21 @@
 [tox]
 envlist=flake8,py3
 
 [testenv:py3]
 deps =
   .[testing]
   pytest-cov
   pifpaf
+setenv =
+  LC_ALL=C.UTF-8
+  LC_CTYPE=C.UTF-8
+  LANG=C.UTF-8
 commands =
   pifpaf run postgresql -- pytest --cov=swh --cov-branch {posargs}
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8