diff --git a/__tests__/config/webpack.js b/__tests__/config/webpack.js
new file mode 100644
index 000000000..262e850ff
--- /dev/null
+++ b/__tests__/config/webpack.js
@@ -0,0 +1,37 @@
+/* eslint-env jest */
+
+const crypto = require('crypto');
+const fs = require('fs');
+const forge = require('node-forge');
+
+jest.unmock('webpack');
+
+const createWebpackConfig = require('../../config/webpack/create');
+
+describe('webpack build information', () => {
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  test('generates a raw 32-byte key accepted by the renderer cipher', () => {
+    const bytes = [
+      0, 10, 13, 34, 92, 255,
+      ...Array.from({ length: 26 }, (_, index) => index + 128),
+    ];
+    jest.spyOn(crypto, 'randomBytes').mockReturnValue(Buffer.from(bytes));
+    const writeFile = jest.spyOn(fs, 'writeFileSync').mockImplementation(() => {});
+
+    const webpackConfig = createWebpackConfig('production');
+
+    const buildInfo = JSON.parse(writeFile.mock.calls[0][1]);
+    const definePlugin = webpackConfig.plugins.find(plugin => (
+      plugin.definitions && plugin.definitions.BUILD_INFO
+    ));
+    const clientBuildInfo = JSON.parse(definePlugin.definitions.BUILD_INFO);
+    expect(buildInfo.key).toHaveLength(32);
+    expect([...buildInfo.key].map(character => character.charCodeAt(0))).toEqual(bytes);
+    expect(clientBuildInfo.key).toBe(buildInfo.key);
+    expect(() => forge.cipher.createCipher('AES-CBC', buildInfo.key)).not.toThrow();
+    expect(() => forge.cipher.createDecipher('AES-CBC', clientBuildInfo.key)).not.toThrow();
+  });
+});
diff --git a/config/webpack/create.js b/config/webpack/create.js
index 2798b2b42..a5b8c2e02 100644
--- a/config/webpack/create.js
+++ b/config/webpack/create.js
@@ -44,7 +44,7 @@ function getBuildInfo(publicPath, keepExisting) {
   }
 
   const info = {
-    key: crypto.randomBytes(32).toString('base64url'),
+    key: crypto.randomBytes(32).toString('latin1'),
     publicPath,
     timestamp: new Date().toISOString(),
     crossOriginLoading: 'anonymous',