diff --git a/tox.ini b/tox.ini
--- a/tox.ini
+++ b/tox.ini
@@ -6,6 +6,10 @@
   .[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}