diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000000000000000000000000000000000000..6e40f46b04f6abac5f646d26da8640345abf20d8
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,9 @@
+import os
+
+import pytest
+
+from . import testutil
+
+@pytest.fixture(scope='session', autouse=True)
+def clean_environment():
+    os.environ.pop('CONSERVANCY_REPOSITORY', None)
diff --git a/tests/test_config.py b/tests/test_config.py
index 589ba456ca4d01b31926ead153fe57985efe80a0..62aea03fb5ad47d3891eafbd811cb42e21de0dfd 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -39,6 +39,5 @@ def test_repository_from_environment():
         assert config.repository_path().parts == ('/', 'usr', 'local')
 
 def test_no_repository():
-    with update_environ(CONSERVANCY_REPOSITORY=None):
-        config = config_mod.Config()
-        assert config.repository_path() is None
+    config = config_mod.Config()
+    assert config.repository_path() is None