diff --git a/browser_patches/firefox/BUILD_NUMBER b/browser_patches/firefox/BUILD_NUMBER
index b493b3aa06..bc58d7a1a9 100644
--- a/browser_patches/firefox/BUILD_NUMBER
+++ b/browser_patches/firefox/BUILD_NUMBER
@@ -1,2 +1,2 @@
-1238
-Changed: lushnikov@chromium.org Wed 17 Mar 2021 12:44:48 AM PDT
+1239
+Changed: ross.wollman@gmail.com Mon Mar 29 00:27:24 PDT 2021
diff --git a/browser_patches/firefox/patches/bootstrap.diff b/browser_patches/firefox/patches/bootstrap.diff
index db7be722cd..03d603b0da 100644
--- a/browser_patches/firefox/patches/bootstrap.diff
+++ b/browser_patches/firefox/patches/bootstrap.diff
@@ -596,7 +596,7 @@ index afa1eee3a6107067be52bf635e94be4271facee0..8d3e7bca533da4e55cc43843de552a12
     * This attempts to save any applicable layout history state (like
     * scroll position) in the nsISHEntry. This is normally done
 diff --git a/dom/base/Document.cpp b/dom/base/Document.cpp
-index 48af2c30f3604a94e6bc1da7848aed3c8ac11c1e..f9c1df0b36b3c9342b81b4c2c7bc7aeca2461f0c 100644
+index 48af2c30f3604a94e6bc1da7848aed3c8ac11c1e..17df24bfdd2d9752686a46b6bb0afc575b091fcb 100644
 --- a/dom/base/Document.cpp
 +++ b/dom/base/Document.cpp
 @@ -3490,6 +3490,9 @@ void Document::SendToConsole(nsCOMArray<nsISecurityConsoleMessage>& aMessages) {
@@ -638,7 +638,7 @@ index 48af2c30f3604a94e6bc1da7848aed3c8ac11c1e..f9c1df0b36b3c9342b81b4c2c7bc7aec
      IgnoreRFP aIgnoreRFP) const {
 +  auto* docShell = static_cast<nsDocShell*>(GetDocShell());
 +  nsIDocShell::ColorSchemeOverride colorScheme;
-+  if (docShell->GetColorSchemeOverride(&colorScheme) == NS_OK &&
++  if (docShell && docShell->GetColorSchemeOverride(&colorScheme) == NS_OK &&
 +      colorScheme != nsIDocShell::COLOR_SCHEME_OVERRIDE_NONE) {
 +    switch (colorScheme) {
 +      case nsIDocShell::COLOR_SCHEME_OVERRIDE_LIGHT:
diff --git a/test/assets/media-query-prefers-color-scheme.svg b/test/assets/media-query-prefers-color-scheme.svg
new file mode 100644
index 0000000000..7b7f1a4947
--- /dev/null
+++ b/test/assets/media-query-prefers-color-scheme.svg
@@ -0,0 +1,8 @@
+<svg viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg">
+  <style>
+    @media (prefers-color-scheme: dark) {
+      * { background-color: blue; }
+    }
+  </style>
+  <circle fill="red" cx="16" cy="16" r="12" />
+</svg>
diff --git a/test/favicon.spec.ts b/test/favicon.spec.ts
new file mode 100644
index 0000000000..c7d9eb4288
--- /dev/null
+++ b/test/favicon.spec.ts
@@ -0,0 +1,61 @@
+/**
+ * Copyright 2018 Google Inc. All rights reserved.
+ * Modifications copyright (c) Microsoft Corporation.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import path from 'path';
+import { it } from './fixtures';
+
+it('should load svg favicon with prefer-color-scheme', (test, {browserName, browserChannel, headful}) => {
+  test.fixme(browserName === 'firefox', 'firefox hard crashes in both headless and headful');
+  test.skip(!headful && browserName !== 'firefox', 'headless browsers, except firefox, do not request favicons');
+  test.skip(headful && browserName === 'webkit' && !browserChannel, 'playwright headful webkit does not have a favicon feature');
+}, async ({page, server}) => {
+  // Browsers aggresively cache favicons, so force bust with the
+  // `d` parameter to make iterating on this test more predictable and isolated.
+  const favicon = `/favicon.svg?d=${Date.now()}`;
+  server.setRoute(favicon, (req, res) => {
+    server.serveFile(req, res, path.join(__dirname, 'assets', 'media-query-prefers-color-scheme.svg'));
+  });
+
+  server.setRoute('/page.html', (_, res) => {
+    res.end(`
+      <!DOCTYPE html>
+      <html>
+        <head>
+          <meta charset="utf-8">
+          <link rel="icon" type="image/svg+xml" href="${favicon}">
+          <title>SVG Favicon Test</title>
+        </head>
+        <body>
+          favicons
+        </body>
+      </html>
+`);
+  });
+
+  await Promise.all([
+    server.waitForRequest(favicon),
+    page.goto(server.PREFIX + '/page.html'),
+  ]);
+
+  // Add artificial delay since, just because we saw the request for the favicon,
+  // it does not mean the browser has processed it. There's not a great way to
+  // hook into something like "favicon is fully displayed" event, so hopefully
+  // 500ms is enough, but not too much!
+  await page.waitForTimeout(500);
+  // Text still being around ensures we haven't actually lost our browser to a crash.
+  await page.waitForSelector('text=favicons');
+});