python · inventshah · Oct 27, 2025 · Oct 27, 2025 · Oct 27, 2025 · Oct 27, 2025
diff --git a/Lib/test/test_io/test_bufferedio.py b/Lib/test/test_io/test_bufferedio.py
@@ -962,6 +962,14 @@ def test_args_error(self):
         with self.assertRaisesRegex(TypeError, "BufferedWriter"):
             self.tp(self.BytesIO(), 1024, 1024, 1024)
 
+    def test_close_without_closed(self):
+        # gh-140650: check TypeError is raised
+        class MockRawIOWithoutClosed(self.MockRawIO):
+            closed = NotImplemented
+
+        bufio = self.tp(MockRawIOWithoutClosed())
+        self.assertRaises(TypeError, bufio.close)
+
 
 class PyBufferedWriterTest(BufferedWriterTest, PyTestCase):
     tp = pyio.BufferedWriter

diff --git a/Misc/NEWS.d/next/Library/2025-10-27-00-40-49.gh-issue-140650.DYJPJ9.rst b/Misc/NEWS.d/next/Library/2025-10-27-00-40-49.gh-issue-140650.DYJPJ9.rst
@@ -0,0 +1,2 @@
+Fix an issue where closing :class:`io.BufferedWriter` could crash
+if the closed attribute had the wrong type.
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
@@ -362,7 +362,7 @@ _enter_buffered_busy(buffered *self)
     }
 
 #define IS_CLOSED(self) \
-    (!self->buffer || \
+    (!self->buffer ? !self->buffer : \
     (self->fast_closed_checks \
      ? _PyFileIO_closed(self->raw) \
      : buffered_closed(self)))
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix an issue where closing :class:`io.BufferedWriter` could crash
		if the closed attribute had the wrong type.