diff --git a/test/test_mediafile_edge.py b/test/test_mediafile_edge.py
index 597f410..219dbaf 100644
--- a/test/test_mediafile_edge.py
+++ b/test/test_mediafile_edge.py
@@ -442,6 +442,10 @@ def test_write(self):
 
     def tearDown(self):
         self.remove_temp_dir()
+        try:
+            del mediafile.MediaFile.read_only_test
+        except AttributeError:
+            pass
 
 
 def suite():