diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py
index da7f40c..a6c0b49 100644
--- a/Lib/test/test_struct.py
+++ b/Lib/test/test_struct.py
@@ -53,6 +53,12 @@
     # The `warnings` module doesn't have an advertised way to restore
     # its filter list.  Cheat.
     save_warnings_filters = warnings.filters[:]
+    # Grrr, we need this function to warn every time.  Without removing
+    # the warningregistry, running test_tarfile then test_struct would fail
+    # on 64-bit platforms.
+    globals = func.func_globals
+    if '__warningregistry__' in globals:
+        del globals['__warningregistry__']
     warnings.filterwarnings("error", r"""^struct.*""", DeprecationWarning)
     warnings.filterwarnings("error", r""".*format requires.*""",
                             DeprecationWarning)