diff --git a/Lib/test/test_unpack.py b/Lib/test/test_unpack.py
index 1c0c523d68..f5ca1d455b 100644
--- a/Lib/test/test_unpack.py
+++ b/Lib/test/test_unpack.py
@@ -1,3 +1,7 @@
+import doctest
+import unittest
+
+
 doctests = """
 
 Unpack tuple
@@ -142,10 +146,26 @@
 
 __test__ = {'doctests' : doctests}
 
-def test_main(verbose=False):
-    from test import support
-    from test import test_unpack
-    support.run_doctest(test_unpack, verbose)
+def load_tests(loader, tests, pattern):
+    tests.addTest(doctest.DocTestSuite())
+    return tests
+
+
+class TestCornerCases(unittest.TestCase):
+    def test_extended_oparg_not_ignored(self):
+        # https://github.com/python/cpython/issues/91625
+        target = "(" + "y,"*400 + ")"
+        code = f"""def unpack_400(x):
+            {target} = x
+            return y
+        """
+        ns = {}
+        exec(code, ns)
+        unpack_400 = ns["unpack_400"]
+        # Warm up the the function for quickening (PEP 659)
+        for _ in range(30):
+            y = unpack_400(range(400))
+            self.assertEqual(y, 399)
 
 if __name__ == "__main__":
-    test_main(verbose=True)
+    unittest.main()