diff --git a/Lib/test/test_structseq.py b/Lib/test/test_structseq.py
index 83c7ccf..02c2f72 100644
--- a/Lib/test/test_structseq.py
+++ b/Lib/test/test_structseq.py
@@ -26,6 +26,12 @@
         for i in xrange(-len(t), len(t)-1):
             self.assertEqual(t[i], astuple[i])
 
+    def test_tuple_subclass(self):
+        # Issue 1820
+        t = time.localtime()
+        s = ('%s ' * len(t)) % t        # This used to fail because t was not a tuple subclass
+        self.assert_(isinstance(t, tuple))
+
     def test_repr(self):
         t = time.gmtime()
         self.assert_(repr(t))