diff --git a/src/core/create_compilers/extract_css.ts b/src/core/create_compilers/extract_css.ts
index e885154..a60d848 100644
--- a/src/core/create_compilers/extract_css.ts
+++ b/src/core/create_compilers/extract_css.ts
@@ -219,7 +219,7 @@ export default function extract_css(client_result: CompileResult, components: Pa
 	});
 
 	unclaimed.forEach(file => {
-		entry_css_modules.push(css_map.get(file));
+		entry_css_modules.push(file);
 	});
 
 	const leftover = get_css_from_modules(entry_css_modules, css_map, dirs);
diff --git a/test/apps/css/rollup.config.js b/test/apps/css/rollup.config.js
new file mode 100644
index 0000000..943b676
--- /dev/null
+++ b/test/apps/css/rollup.config.js
@@ -0,0 +1,64 @@
+import resolve from 'rollup-plugin-node-resolve';
+import replace from 'rollup-plugin-replace';
+import svelte from 'rollup-plugin-svelte';
+
+const mode = process.env.NODE_ENV;
+const dev = mode === 'development';
+
+const config = require('../../../config/rollup.js');
+
+export default {
+	client: {
+		input: config.client.input(),
+		output: config.client.output(),
+		plugins: [
+			replace({
+				'process.browser': true,
+				'process.env.NODE_ENV': JSON.stringify(mode)
+			}),
+			svelte({
+				dev,
+				hydratable: true,
+				emitCss: true
+			}),
+			resolve()
+		],
+
+		// temporary, pending Rollup 1.0
+		experimentalCodeSplitting: true
+	},
+
+	server: {
+		input: config.server.input(),
+		output: config.server.output(),
+		plugins: [
+			replace({
+				'process.browser': false,
+				'process.env.NODE_ENV': JSON.stringify(mode)
+			}),
+			svelte({
+				generate: 'ssr',
+				dev
+			}),
+			resolve({
+				preferBuiltins: true
+			})
+		],
+		external: ['sirv', 'polka'],
+
+		// temporary, pending Rollup 1.0
+		experimentalCodeSplitting: true
+	},
+
+	serviceworker: {
+		input: config.serviceworker.input(),
+		output: config.serviceworker.output(),
+		plugins: [
+			resolve(),
+			replace({
+				'process.browser': true,
+				'process.env.NODE_ENV': JSON.stringify(mode)
+			})
+		]
+	}
+};
\ No newline at end of file
diff --git a/test/apps/css/src/client.js b/test/apps/css/src/client.js
new file mode 100644
index 0000000..0865a4a
--- /dev/null
+++ b/test/apps/css/src/client.js
@@ -0,0 +1,9 @@
+import * as sapper from '../__sapper__/client.js';
+
+window.start = () => sapper.start({
+	target: document.querySelector('#sapper')
+});
+
+window.prefetchRoutes = () => sapper.prefetchRoutes();
+window.prefetch = href => sapper.prefetch(href);
+window.goto = href => sapper.goto(href);
\ No newline at end of file
diff --git a/test/apps/css/src/routes/_components/Title.html b/test/apps/css/src/routes/_components/Title.html
new file mode 100644
index 0000000..05cf195
--- /dev/null
+++ b/test/apps/css/src/routes/_components/Title.html
@@ -0,0 +1,7 @@
+<h1>Title</h1>
+
+<style>
+	h1 {
+		color: green;
+	}
+</style>
\ No newline at end of file
diff --git a/test/apps/css/src/routes/_error.html b/test/apps/css/src/routes/_error.html
new file mode 100644
index 0000000..4cd55d2
--- /dev/null
+++ b/test/apps/css/src/routes/_error.html
@@ -0,0 +1,3 @@
+<h1>{status}</h1>
+
+<p>{error.message}</p>
\ No newline at end of file
diff --git a/test/apps/css/src/routes/bar.html b/test/apps/css/src/routes/bar.html
new file mode 100644
index 0000000..876ee63
--- /dev/null
+++ b/test/apps/css/src/routes/bar.html
@@ -0,0 +1,11 @@
+<svelte:component this={Title}/>
+
+<script>
+	export default {
+		oncreate() {
+			import('./_components/Title.html').then(({ default: Title }) => {
+				this.set({ Title });
+			});
+		}
+	};
+</script>
\ No newline at end of file
diff --git a/test/apps/css/src/routes/foo.html b/test/apps/css/src/routes/foo.html
new file mode 100644
index 0000000..3aeeeeb
--- /dev/null
+++ b/test/apps/css/src/routes/foo.html
@@ -0,0 +1,7 @@
+<h1>Foo</h1>
+
+<style>
+	h1 {
+		color: blue;
+	}
+</style>
\ No newline at end of file
diff --git a/test/apps/css/src/routes/index.html b/test/apps/css/src/routes/index.html
new file mode 100644
index 0000000..a9fd9fd
--- /dev/null
+++ b/test/apps/css/src/routes/index.html
@@ -0,0 +1,10 @@
+<h1>Great success!</h1>
+
+<a href="foo">foo</a>
+<a href="bar">bar</a>
+
+<style>
+	h1 {
+		color: red;
+	}
+</style>
\ No newline at end of file
diff --git a/test/apps/css/src/server.js b/test/apps/css/src/server.js
new file mode 100644
index 0000000..0e7741c
--- /dev/null
+++ b/test/apps/css/src/server.js
@@ -0,0 +1,8 @@
+import polka from 'polka';
+import * as sapper from '../__sapper__/server.js';
+
+const { PORT } = process.env;
+
+polka()
+	.use(sapper.middleware())
+	.listen(PORT);
diff --git a/test/apps/css/src/service-worker.js b/test/apps/css/src/service-worker.js
new file mode 100644
index 0000000..9d2ac9d
--- /dev/null
+++ b/test/apps/css/src/service-worker.js
@@ -0,0 +1,82 @@
+import { timestamp, files, shell, routes } from '../__sapper__/service-worker.js';
+
+const ASSETS = `cache${timestamp}`;
+
+// `shell` is an array of all the files generated by webpack,
+// `files` is an array of everything in the `static` directory
+const to_cache = shell.concat(ASSETS);
+const cached = new Set(to_cache);
+
+self.addEventListener('install', event => {
+	event.waitUntil(
+		caches
+			.open(ASSETS)
+			.then(cache => cache.addAll(to_cache))
+			.then(() => {
+				self.skipWaiting();
+			})
+	);
+});
+
+self.addEventListener('activate', event => {
+	event.waitUntil(
+		caches.keys().then(async keys => {
+			// delete old caches
+			for (const key of keys) {
+				if (key !== ASSETS) await caches.delete(key);
+			}
+
+			self.clients.claim();
+		})
+	);
+});
+
+self.addEventListener('fetch', event => {
+	if (event.request.method !== 'GET') return;
+
+	const url = new URL(event.request.url);
+
+	// don't try to handle e.g. data: URIs
+	if (!url.protocol.startsWith('http')) return;
+
+	// ignore dev server requests
+	if (url.hostname === self.location.hostname && url.port !== self.location.port) return;
+
+	// always serve assets and webpack-generated files from cache
+	if (url.host === self.location.host && cached.has(url.pathname)) {
+		event.respondWith(caches.match(event.request));
+		return;
+	}
+
+	// for pages, you might want to serve a shell `index.html` file,
+	// which Sapper has generated for you. It's not right for every
+	// app, but if it's right for yours then uncomment this section
+	/*
+	if (url.origin === self.origin && routes.find(route => route.pattern.test(url.pathname))) {
+		event.respondWith(caches.match('/index.html'));
+		return;
+	}
+	*/
+
+	if (event.request.cache === 'only-if-cached') return;
+
+	// for everything else, try the network first, falling back to
+	// cache if the user is offline. (If the pages never change, you
+	// might prefer a cache-first approach to a network-first one.)
+	event.respondWith(
+		caches
+			.open(`offline${timestamp}`)
+			.then(async cache => {
+				try {
+					const response = await fetch(event.request);
+					cache.put(event.request, response.clone());
+					return response;
+				} catch(err) {
+					const response = await cache.match(event.request);
+					if (response) return response;
+
+					throw err;
+				}
+			})
+	);
+});
diff --git a/test/apps/css/src/template.html b/test/apps/css/src/template.html
new file mode 100644
index 0000000..0eb1f3b
--- /dev/null
+++ b/test/apps/css/src/template.html
@@ -0,0 +1,14 @@
+<!doctype html>
+<html lang="en">
+<head>
+	<meta charset='utf-8'>
+
+	%sapper.base%
+	%sapper.styles%
+	%sapper.head%
+</head>
+<body>
+	<div id='sapper'>%sapper.html%</div>
+	%sapper.scripts%
+</body>
+</html>
diff --git a/test/apps/css/test.ts b/test/apps/css/test.ts
new file mode 100644
index 0000000..c6539af
--- /dev/null
+++ b/test/apps/css/test.ts
@@ -0,0 +1,78 @@
+import * as assert from 'assert';
+import * as puppeteer from 'puppeteer';
+import { build } from '../../../api';
+import { AppRunner } from '../AppRunner';
+import { wait } from '../../utils';
+
+describe('css', function() {
+	this.timeout(10000);
+
+	let runner: AppRunner;
+	let page: puppeteer.Page;
+	let base: string;
+
+	// helpers
+	let start: () => Promise<void>;
+	let prefetchRoutes: () => Promise<void>;
+	let prefetch: (href: string) => Promise<void>;
+	let goto: (href: string) => Promise<void>;
+	let title: () => Promise<string>;
+
+	// hooks
+	before(async () => {
+		await build({ cwd: __dirname });
+
+		runner = new AppRunner(__dirname, '__sapper__/build/server/server.js');
+		({ base, page, start, prefetchRoutes, prefetch, goto, title } = await runner.start());
+	});
+
+	after(() => runner.end());
+
+	it('includes critical CSS with server render', async () => {
+		await page.goto(base);
+
+		assert.equal(
+			await page.evaluate(() => {
+				const h1 = document.querySelector('h1');
+				return getComputedStyle(h1).color;
+			}),
+			'rgb(255, 0, 0)'
+		);
+	});
+
+	it('loads CSS when navigating client-side', async () => {
+		await page.goto(base);
+
+		await start();
+		await prefetchRoutes();
+
+		await page.click(`[href="foo"]`);
+		await wait(50);
+
+		assert.equal(
+			await page.evaluate(() => {
+				const h1 = document.querySelector('h1');
+				return getComputedStyle(h1).color;
+			}),
+			'rgb(0, 0, 255)'
+		);
+	});
+
+	it('loads CSS for a lazily-rendered component', async () => {
+		await page.goto(base);
+
+		await start();
+		await prefetchRoutes();
+
+		await page.click(`[href="bar"]`);
+		await wait(50);
+
+		assert.equal(
+			await page.evaluate(() => {
+				const h1 = document.querySelector('h1');
+				return getComputedStyle(h1).color;
+			}),
+			'rgb(0, 128, 0)'
+		);
+	});
+});
\ No newline at end of file