diff -r a4fe32477df6 Lib/test/multibytecodec_support.py
--- a/Lib/test/multibytecodec_support.py	Wed Jul 15 11:51:22 2015 +1200
+++ b/Lib/test/multibytecodec_support.py	Thu Jul 16 12:47:15 2015 -0400
@@ -269,6 +269,18 @@
                         ostream.write(data)
 
                 self.assertEqual(ostream.getvalue(), self.tstring[0])
+                ostream.reset()
+
+    def test_streamwriter_hreset(self):
+        # Don't segfault when calling MultibyteStreamWriter.reset()
+        # issue issue23247
+        stream = self.writer(BytesIO())
+        stream.reset()
+
+        for data in self.tstring:
+            stream = self.writer(BytesIO())
+            stream.write(data)
+            stream.reset()
 
 
 class TestBase_Mapping(unittest.TestCase):
diff -r a4fe32477df6 Modules/cjkcodecs/multibytecodec.c
--- a/Modules/cjkcodecs/multibytecodec.c	Wed Jul 15 11:51:22 2015 +1200
+++ b/Modules/cjkcodecs/multibytecodec.c	Thu Jul 16 12:47:15 2015 -0400
@@ -1685,6 +1685,10 @@
 {
     PyObject *pwrt;
 
+    if (self->pending == NULL) {
+        Py_RETURN_NONE;
+    }
+
     pwrt = multibytecodec_encode(self->codec, &self->state,
                     self->pending, NULL, self->errors,
                     MBENC_FLUSH | MBENC_RESET);