diff --git a/swh/core/tests/conftest.py b/swh/core/tests/conftest.py
new file mode 100644
index 0000000..5d8dcd5
--- /dev/null
+++ b/swh/core/tests/conftest.py
@@ -0,0 +1,2 @@
+import os
+os.environ['LC_ALL'] = 'C.UTF-8'