diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index f12f911..847c7a6 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -909,6 +909,15 @@
             with self.assertRaises(ValueError):
                 b[3:4] = elem
 
+    def test_setslice_extend(self):
+        # Exercise the resizing logic (see issue #19087)
+        b = bytearray(range(100))
+        self.assertEqual(list(b), list(range(100)))
+        del b[:10]
+        self.assertEqual(list(b), list(range(10, 100)))
+        b.extend(range(100, 110))
+        self.assertEqual(list(b), list(range(10, 110)))
+
     def test_extended_set_del_slice(self):
         indices = (0, None, 1, 3, 19, 300, 1<<333, -1, -2, -31, -300)
         for start in indices:
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 30eca4a..70b55b2 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -721,7 +721,7 @@
         samples = [b'', b'u'*100000]
         for sample in samples:
             x = bytearray(sample)
-            check(x, vsize('inP') + x.__alloc__())
+            check(x, vsize('n2Pi') + x.__alloc__())
         # bytearray_iterator
         check(iter(bytearray()), size('nP'))
         # cell