diff --git a/lualib/core/http/h2stream.lua b/lualib/core/http/h2stream.lua
index 483c71d..2ac1771 100644
--- a/lualib/core/http/h2stream.lua
+++ b/lualib/core/http/h2stream.lua
@@ -357,7 +357,8 @@ local function frame_winupdate(ch, id, flag, dat)
 		if n > 0 then
 			local dat = remove(ch, 1)
 			if dat then
-				n = n - #dat
+				local len = remove(ch, 1)
+				n = n - len
 				ch.socket:write(dat)
 			end
 		end
@@ -440,7 +441,6 @@ local function handshake_as_client(ch, socket)
 	end
 	frame_settings(ch, id, f, dat)
 	write(socket, build_setting(0x01))
-	write(socket, build_winupdate(0, 0, 1*1024*1024))
 	while true do
 		local t,f,dat,id = read_frame(socket)
 		if not t then
@@ -479,7 +479,6 @@ local function handshake_as_server(socket, ch)
 	end
 	frame_settings(ch, id, f, dat)
 	write(socket, build_setting(0x01))
-	write(socket, build_winupdate(0, 0, 1*1024*1024))
 	while true do
 		local t,f,dat,id = read_frame(socket)
 		if not t then
@@ -726,13 +725,15 @@ local function write_func(close)
 			end
 		end
 		dat = dat or ""
+		local body_len = #dat
 		dat = build_body(s.id, ch.frame_max_size, dat, close)
 		local win = ch.window_size
 		if win <= 0 then
 			ch[#ch + 1] = dat
+			ch[#ch + 1] = body_len
 			return true, "ok"
 		else
-			ch.window_size = win - #dat
+			ch.window_size = win - body_len
 			return ch.socket:write(dat)
 		end
 	end
diff --git a/test/testhttp2.lua b/test/testhttp2.lua
index be25e82..fea9dd2 100644
--- a/test/testhttp2.lua
+++ b/test/testhttp2.lua
@@ -6,6 +6,38 @@ local testaux = require "test.testaux"
 
 local f<const> = io.open("./a.txt", "w")
 
+local data = crypto.randomkey(65*1024)
+
+local alpn_protos = {"http/1.1", "h2"}
+local function POST(url, header, body)
+	if body then
+		header = header or {}
+		header["content-length"] = #body * 2
+	end
+	local stream<close>, err = http.request("POST", url, header, false, alpn_protos)
+	if not stream then
+		return nil, err
+	end
+	local version = stream.version
+	if version == "HTTP/2" then
+		stream:write(body)
+		stream:close(body)
+	else
+		stream:write(body)
+	end
+	local status, header = stream:readheader()
+	if not status then
+		return nil, header
+	end
+	testaux.asserteq(stream.channel.window_size, 65535, "http2.client window_size")
+	local body = stream:readall()
+	return {
+		status = status,
+		header = header,
+		body = body,
+	}
+end
+
 if not crypto.digestsign then
 	print("not enable openssl")
 	return
@@ -29,7 +61,7 @@ http.listen {
 		testaux.asserteq(stream.path, "/test", "http2.server path")
 		testaux.asserteq(header['hello'], "world", "http2.server header")
 		local body = stream:readall()
-		testaux.asserteq(body, "http2", "http2 body")
+		testaux.asserteq(body, data .. data, "http2 body")
 		stream:respond(200, {["foo"] = header['foo']})
 		stream:close("http2")
 	end
@@ -62,14 +94,14 @@ print("test http2 server")
 local wg = waitgroup:create()
 for i = 1, 2000 do
 	wg:fork(function()
-		local key = crypto.randomkey(1028)
-		local ack, err = http.POST("https://localhost:8082/test", {
-			['hello'] = 'world',
-			['foo'] = key,
-		}, "http2")
-		testaux.asserteq(ack.status, 200, "http2.client status")
-		testaux.asserteq(ack.header['foo'], key, "http2.client header")
-		testaux.asserteq(ack.body, 'http2', "http2.client body")
+	local key = crypto.randomkey(1028)
+		local ack, err = POST("https://localhost:8082/test", {
+		['hello'] = 'world',
+		['foo'] = key,
+	}, data)
+	testaux.asserteq(ack.status, 200, "http2.client status")
+	testaux.asserteq(ack.header['foo'], key, "http2.client header")
+	testaux.asserteq(ack.body, 'http2', "http2.client body")
 	end)
 end
 wg:wait()