diff --git a/doc/python.rst b/doc/python.rst
index a079c590..357e7b3a 100644
--- a/doc/python.rst
+++ b/doc/python.rst
@@ -448,6 +448,17 @@ Session objects
     The :py:class:`InvalidArgumentError` will be raised if the *iv*
     contains duplicate settings ID or invalid value.
 
+.. py:method:: Session.submit_window_update(stream_id, delta_window_size)
+
+    Submits WINDOW_UPDATE frame. The effective range of the
+    *delta_window_size* is ``[1, (1 << 31)-1]``, inclusive. But the
+    application must be responsible to keep the resulting window
+    ``size <= (1 << 31)-1``.
+
+    The :py:class:`InvalidArgumentError` will be raised if the
+    *delta_window_size* is 0 or negative. The
+    :py:class:`StreamClosedError` will be raised if the stream is
+    already closed or does not exist.
 
 Frame Types
 -----------
diff --git a/python/cspdylay.pxd b/python/cspdylay.pxd
index 5435f0c5..f993e327 100644
--- a/python/cspdylay.pxd
+++ b/python/cspdylay.pxd
@@ -128,6 +128,11 @@ cdef extern from 'spdylay/spdylay.h':
         int32_t last_good_stream_id
         uint32_t status_code
 
+    ctypedef struct spdylay_window_update:
+        spdylay_ctrl_hd hd
+        int32_t stream_id
+        int32_t delta_window_size
+
     ctypedef union spdylay_frame:
         spdylay_syn_stream syn_stream
         spdylay_syn_reply syn_reply
@@ -136,7 +141,7 @@ cdef extern from 'spdylay/spdylay.h':
         spdylay_ping ping
         spdylay_goaway goaway
         spdylay_headers headers
-        #spdylay_window_update window_update
+        spdylay_window_update window_update
         #spdylay_credential credential
 
     ctypedef union spdylay_data_source:
@@ -257,3 +262,7 @@ cdef extern from 'spdylay/spdylay.h':
 
     int spdylay_submit_settings(spdylay_session *session, uint8_t flags,
                                 spdylay_settings_entry *iv, size_t niv)
+
+    int spdylay_submit_window_update(spdylay_session *session,
+                                     int32_t stream_id,
+                                     int32_t delta_window_size)
diff --git a/python/spdylay.pyx b/python/spdylay.pyx
index f1ee17a5..45c3a4ac 100644
--- a/python/spdylay.pyx
+++ b/python/spdylay.pyx
@@ -22,6 +22,9 @@ class ZlibError(Exception):
 class UnsupportedVersionError(Exception):
     pass
 
+class StreamClosedError(Exception):
+    pass
+
 class DataProvider:
     def __init__(self, source, read_cb):
         self.source = source
@@ -183,6 +186,24 @@ cdef class GoawayFrame(CtrlFrame):
         def __get__(self):
             return self.status_code
 
+cdef class WindowUpdateFrame(CtrlFrame):
+    cdef int32_t stream_id
+    cdef int32_t delta_window_size
+
+    cdef void fill(self, cspdylay.spdylay_window_update *frame):
+        self.fillhd(&frame.hd)
+
+        self.stream_id = frame.stream_id
+        self.delta_window_size = frame.delta_window_size
+
+    property stream_id:
+        def __get__(self):
+            return self.stream_id
+
+    property delta_window_size:
+        def __get__(self):
+            return self.delta_window_size
+
 cdef object cnv2pynv(char **nv):
     ''' Convert C-style name/value pairs ``nv`` to Python style
     pairs. '''
@@ -253,6 +274,7 @@ cdef void on_ctrl_recv_callback(cspdylay.spdylay_session *session,
     cdef SettingsFrame settings
     cdef PingFrame ping
     cdef GoawayFrame goaway
+    cdef WindowUpdateFrame window_update
 
     cdef Session pysession = <Session>user_data
 
@@ -288,6 +310,10 @@ cdef void on_ctrl_recv_callback(cspdylay.spdylay_session *session,
         goaway = GoawayFrame()
         goaway.fill(&frame.goaway)
         pyframe = goaway
+    elif frame_type == cspdylay.SPDYLAY_WINDOW_UPDATE:
+        window_update = WindowUpdateFrame()
+        window_update.fill(&frame.window_update)
+        pyframe = window_update
 
     if pyframe:
         try:
@@ -739,6 +765,19 @@ cdef class Session:
         elif rv == cspdylay.SPDYLAY_ERR_NOMEM:
             raise MemoryError()
 
+    cpdef submit_window_update(self, stream_id, delta_window_size):
+        cdef int rv
+        rv = cspdylay.spdylay_submit_window_update(self._c_session, stream_id,
+                                                   delta_window_size)
+        if rv == 0:
+            return
+        elif rv == cspdylay.SPDYLAY_ERR_INVALID_ARGUMENT:
+            raise InvalidArgumentError()
+        elif rv == cspdylay.SPDYLAY_ERR_STREAM_CLOSED:
+            raise StreamClosedError()
+        elif rv == cspdylay.SPDYLAY_ERR_NOMEM:
+            raise MemoryError()
+
     cpdef submit_settings(self, flags, iv):
         ''' Submit SETTINGS frame. iv is list of tuple (settings_id,
         flag, value)
diff --git a/python/spdylay_tests.py b/python/spdylay_tests.py
index fa4ec632..9e6b1f1c 100644
--- a/python/spdylay_tests.py
+++ b/python/spdylay_tests.py
@@ -314,5 +314,26 @@ class SpdylayTests(unittest.TestCase):
         self.assertEqual(spdylay.PING, frame.frame_type)
         self.assertEqual(1, frame.unique_id)
 
+    def test_submit_window_update(self):
+        self.client_session.submit_syn_stream(spdylay.CTRL_FLAG_NONE, 0, 2,
+                                              [(b':path', b'/')], None)
+        self.client_session.send()
+        self.server_session.recv()
+
+        self.assertEqual(1, len(self.server_streams.recv_frames))
+        frame = self.server_streams.recv_frames[0]
+        self.assertEqual(spdylay.SYN_STREAM, frame.frame_type)
+        self.assertEqual(1, frame.stream_id)
+
+        self.server_session.submit_window_update(1, 4096)
+        self.server_session.send()
+        self.client_session.recv()
+
+        self.assertEqual(1, len(self.client_streams.recv_frames))
+        frame = self.client_streams.recv_frames[0]
+        self.assertEqual(spdylay.WINDOW_UPDATE, frame.frame_type)
+        self.assertEqual(1, frame.stream_id)
+        self.assertEqual(4096, frame.delta_window_size)
+
 if __name__ == '__main__':
     unittest.main()