diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index bc59af3..936dbed 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -793,6 +793,16 @@
         bufio.__init__(rawio)
         self.assertEqual(b"abc", bufio.read())
 
+    def test_uninitialized(self):
+        bufio = self.tp.__new__(self.tp)
+        del bufio
+        bufio = self.tp.__new__(self.tp)
+        self.assertRaisesRegexp((ValueError, AttributeError),
+                                'uninitialized|has no attribute',
+                                bufio.read, 0)
+        bufio.__init__(self.MockRawIO())
+        self.assertEqual(bufio.read(0), b'')
+
     def test_read(self):
         for arg in (None, 7):
             rawio = self.MockRawIO((b"abc", b"d", b"efg"))
@@ -1029,6 +1039,16 @@
         bufio.flush()
         self.assertEqual(b"".join(rawio._write_stack), b"abcghi")
 
+    def test_uninitialized(self):
+        bufio = self.tp.__new__(self.tp)
+        del bufio
+        bufio = self.tp.__new__(self.tp)
+        self.assertRaisesRegexp((ValueError, AttributeError),
+                                'uninitialized|has no attribute',
+                                bufio.write, b'')
+        bufio.__init__(self.MockRawIO())
+        self.assertEqual(bufio.write(b''), 0)
+
     def test_detach_flush(self):
         raw = self.MockRawIO()
         buf = self.tp(raw)
@@ -1313,6 +1333,20 @@
         pair = self.tp(self.MockRawIO(), self.MockRawIO())
         self.assertFalse(pair.closed)
 
+    def test_uninitialized(self):
+        pair = self.tp.__new__(self.tp)
+        del pair
+        pair = self.tp.__new__(self.tp)
+        self.assertRaisesRegexp((ValueError, AttributeError),
+                                'uninitialized|has no attribute',
+                                pair.read, 0)
+        self.assertRaisesRegexp((ValueError, AttributeError),
+                                'uninitialized|has no attribute',
+                                pair.write, b'')
+        pair.__init__(self.MockRawIO(), self.MockRawIO())
+        self.assertEqual(pair.read(0), b'')
+        self.assertEqual(pair.write(b''), 0)
+
     def test_detach(self):
         pair = self.tp(self.MockRawIO(), self.MockRawIO())
         self.assertRaises(self.UnsupportedOperation, pair.detach)
@@ -1440,6 +1474,10 @@
         BufferedReaderTest.test_constructor(self)
         BufferedWriterTest.test_constructor(self)
 
+    def test_uninitialized(self):
+        BufferedReaderTest.test_uninitialized(self)
+        BufferedWriterTest.test_uninitialized(self)
+
     def test_read_and_write(self):
         raw = self.MockRawIO((b"asdf", b"ghjk"))
         rw = self.tp(raw, 8)