diff --git a/tests/test_pub1c-rest.py b/tests/test_pub1c-rest.py
index 6aa8b4b..0fed42f 100644
--- a/tests/test_pub1c-rest.py
+++ b/tests/test_pub1c-rest.py
@@ -38,7 +38,7 @@ def temp_config(tmpdir) -> str:
 
 @pytest.fixture
 def flask_app(temp_config) -> Flask:
-    os.putenv('WEBPUB1C_CONFIG', temp_config)
+    os.environ['WEBPUB1C_CONFIG'] = temp_config
     pub1c = importlib.import_module('pub1c-rest')
     return pub1c.app