diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 877d3b5..c204a82 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -1439,6 +1439,22 @@ class CBufferedReaderTest(BufferedReaderTest, SizeofTest):
         with self.assertRaisesRegex(TypeError, "BufferedReader"):
             self.tp(io.BytesIO(), 1024, 1024, 1024)
 
+    def test_bad_readinto_value(self):
+        rawio = io.BufferedReader(io.BytesIO(b"12"))
+        rawio.readinto = lambda buf: -1
+        bufio = self.tp(rawio)
+        with self.assertRaises(OSError) as cm:
+            bufio.readline()
+        assert cm.exception.__cause__ is None
+
+    def test_bad_readinto_type(self):
+        rawio = io.BufferedReader(io.BytesIO(b"12"))
+        rawio.readinto = lambda buf: b''
+        bufio = self.tp(rawio)
+        with self.assertRaises(TypeError) as cm:
+            bufio.readline()
+        assert isinstance(cm.exception.__cause__, TypeError)
+
 
 class PyBufferedReaderTest(BufferedReaderTest):
     tp = pyio.BufferedReader
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index c760522..e0c27d9 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -1496,6 +1496,14 @@ _bufferedreader_raw_read(buffered *self, char *start, Py_ssize_t len)
     }
     n = PyNumber_AsSsize_t(res, PyExc_ValueError);
     Py_DECREF(res);
+
+    if (n == -1 && PyErr_Occurred()) {
+        _PyErr_TrySetFromCause(
+            "raw readinto() returned invalid value"
+        );
+        return -1;
+    }
+
     if (n < 0 || n > len) {
         PyErr_Format(PyExc_IOError,
                      "raw readinto() returned invalid length %zd "