diff --git a/parfive/tests/test_downloader.py b/parfive/tests/test_downloader.py
index 1766fae..b6c8b0a 100644
--- a/parfive/tests/test_downloader.py
+++ b/parfive/tests/test_downloader.py
@@ -521,7 +521,10 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
     def run(self):
-        self.result = self._target(*self._args, **self._kwargs)
+        try:
+            self.result = self._target(*self._args, **self._kwargs)
+        finally:
+            del self._target, self._args, self._kwargs
 
 
 @skip_windows