diff --git a/tests/functional/test_config.py b/tests/functional/test_config.py
index b9a466d32b..2c31d22381 100644
--- a/tests/functional/test_config.py
+++ b/tests/functional/test_config.py
@@ -144,6 +144,8 @@ def run_test(cls: Callable, attr: str, name: str, value: str, expected: Any = No
         finally:
             if before is not None:
                 os.environ[name] = before
+            else:
+                os.environ.pop(name, None)
 
     # Test different config classes.
     run_test(ApeConfig, "contracts_folder", "APE_CONTRACTS_FOLDER", "3465220869b2")