diff --git a/server/render.js b/server/render.js
index 699eef4f..eabcd659 100644
--- a/server/render.js
+++ b/server/render.js
@@ -185,7 +185,9 @@ export function sendHTML (req, res, html, method, { dev }) {
   }
 
   res.setHeader('ETag', etag)
-  res.setHeader('Content-Type', 'text/html')
+  if (!res.getHeader('Content-Type')) {
+    res.setHeader('Content-Type', 'text/html')
+  }
   res.setHeader('Content-Length', Buffer.byteLength(html))
   res.end(method === 'HEAD' ? null : html)
 }
diff --git a/test/integration/basic/pages/custom-encoding.js b/test/integration/basic/pages/custom-encoding.js
new file mode 100644
index 00000000..e091c3c0
--- /dev/null
+++ b/test/integration/basic/pages/custom-encoding.js
@@ -0,0 +1,13 @@
+import React from 'react'
+export default class extends React.Component {
+  static async getInitialProps ({res}) {
+    if (res) {
+      res.setHeader('Content-Type', 'text/html; charset=utf-8')
+    }
+    return {}
+  }
+
+  render () {
+    return null
+  }
+}
diff --git a/test/integration/basic/test/index.test.js b/test/integration/basic/test/index.test.js
index 5ff68a11..265e31d9 100644
--- a/test/integration/basic/test/index.test.js
+++ b/test/integration/basic/test/index.test.js
@@ -3,6 +3,7 @@
 import { join } from 'path'
 import {
   renderViaHTTP,
+  fetchViaHTTP,
   findPort,
   launchApp,
   killApp
@@ -55,7 +56,7 @@ describe('Basic Features', () => {
   })
   afterAll(() => killApp(context.server))
 
-  rendering(context, 'Rendering via HTTP', (p, q) => renderViaHTTP(context.appPort, p, q))
+  rendering(context, 'Rendering via HTTP', (p, q) => renderViaHTTP(context.appPort, p, q), (p, q) => fetchViaHTTP(context.appPort, p, q))
   clientNavigation(context, (p, q) => renderViaHTTP(context.appPort, p, q))
   dynamic(context, (p, q) => renderViaHTTP(context.appPort, p, q))
   hmr(context, (p, q) => renderViaHTTP(context.appPort, p, q))
diff --git a/test/integration/basic/test/rendering.js b/test/integration/basic/test/rendering.js
index 21a85c6e..47391034 100644
--- a/test/integration/basic/test/rendering.js
+++ b/test/integration/basic/test/rendering.js
@@ -2,7 +2,7 @@
 
 import cheerio from 'cheerio'
 
-export default function ({ app }, suiteName, render) {
+export default function ({ app }, suiteName, render, fetch) {
   async function get$ (path, query) {
     const html = await render(path, query)
     return cheerio.load(html)
@@ -63,6 +63,16 @@ export default function ({ app }, suiteName, render) {
       expect($('pre').text().includes(expectedErrorMessage)).toBeTruthy()
     })
 
+    test('default Content-Type', async () => {
+      const res = await fetch('/stateless')
+      expect(res.headers.get('Content-Type')).toMatch('text/html')
+    })
+
+    test('setting Content-Type in getInitialProps', async () => {
+      const res = await fetch('/custom-encoding')
+      expect(res.headers.get('Content-Type')).toMatch('text/html; charset=utf-8')
+    })
+
     test('allows to import .json files', async () => {
       const html = await render('/json')
       expect(html.includes('Zeit')).toBeTruthy()
diff --git a/test/integration/production/test/index.test.js b/test/integration/production/test/index.test.js
index 5128f707..09854e66 100644
--- a/test/integration/production/test/index.test.js
+++ b/test/integration/production/test/index.test.js
@@ -117,6 +117,9 @@ describe('Production Usage', () => {
       const req = { url: '/stateless', headers: {} }
       const headers = {}
       const res = {
+        getHeader (key) {
+          return headers[key]
+        },
         setHeader (key, value) {
           headers[key] = value
         },
@@ -132,6 +135,9 @@ describe('Production Usage', () => {
       const originalConfigValue = app.config.poweredByHeader
       app.config.poweredByHeader = false
       const res = {
+        getHeader () {
+          return false
+        },
         setHeader (key, value) {
           if (key === 'X-Powered-By') {
             throw new Error('Should not set the X-Powered-By header')
diff --git a/test/lib/next-test-utils.js b/test/lib/next-test-utils.js
index a8ac957b..60eadff2 100644
--- a/test/lib/next-test-utils.js
+++ b/test/lib/next-test-utils.js
@@ -23,8 +23,12 @@ export function renderViaAPI (app, pathname, query) {
 }
 
 export function renderViaHTTP (appPort, pathname, query) {
+  return fetchViaHTTP(appPort, pathname, query).then((res) => res.text())
+}
+
+export function fetchViaHTTP (appPort, pathname, query) {
   const url = `http://localhost:${appPort}${pathname}${query ? `?${qs.stringify(query)}` : ''}`
-  return fetch(url).then((res) => res.text())
+  return fetch(url)
 }
 
 export function findPort () {
diff --git a/yarn.lock b/yarn.lock
index b124f165..df5aad7c 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -6071,9 +6071,9 @@ strip-json-comments@~2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/strip-json-comments/-/strip-json-comments-2.0.1.tgz#3c531942e908c2697c0ec344858c286c7ca0a60a"
 
-styled-jsx@2.1.1:
-  version "2.1.1"
-  resolved "https://registry.yarnpkg.com/styled-jsx/-/styled-jsx-2.1.1.tgz#e7481c7554df50d605cdc84a4e53c58fec3449b5"
+styled-jsx@2.1.2:
+  version "2.1.2"
+  resolved "https://registry.yarnpkg.com/styled-jsx/-/styled-jsx-2.1.2.tgz#c84823402678022355b090d98d959ba126b97911"
   dependencies:
     babel-plugin-syntax-jsx "6.18.0"
     babel-types "6.23.0"