diff --git a/lib/Server.js b/lib/Server.js
index b5444d6eb6..0058ebfd47 100644
--- a/lib/Server.js
+++ b/lib/Server.js
@@ -24,6 +24,7 @@ const webpack = require('webpack');
 const webpackDevMiddleware = require('webpack-dev-middleware');
 const validateOptions = require('schema-utils');
 const isAbsoluteUrl = require('is-absolute-url');
+const normalizeOptions = require('./utils/normalizeOptions');
 const updateCompiler = require('./utils/updateCompiler');
 const createLogger = require('./utils/createLogger');
 const getCertificate = require('./utils/getCertificate');
@@ -58,31 +59,22 @@ class Server {
     this.compiler = compiler;
     this.options = options;
 
-    // Setup default value
-    this.options.contentBase =
-      this.options.contentBase !== undefined
-        ? this.options.contentBase
-        : process.cwd();
-
     this.log = _log || createLogger(options);
 
-    // set serverMode default
-    if (this.options.serverMode === undefined) {
-      this.options.serverMode = 'sockjs';
-    } else {
+    if (this.options.serverMode !== undefined) {
       this.log.warn(
         'serverMode is an experimental option, meaning its usage could potentially change without warning'
       );
     }
-    // set clientMode default
-    if (this.options.clientMode === undefined) {
-      this.options.clientMode = 'sockjs';
-    } else {
+
+    if (this.options.clientMode !== undefined) {
       this.log.warn(
         'clientMode is an experimental option, meaning its usage could potentially change without warning'
       );
     }
 
+    normalizeOptions(this.compiler, this.options);
+
     updateCompiler(this.compiler, this.options);
 
     // this.SocketServerImplementation is a class, so it must be instantiated before use
@@ -112,10 +104,6 @@ class Server {
     this.allowedHosts = this.options.allowedHosts;
     this.disableHostCheck = !!this.options.disableHostCheck;
 
-    if (!this.options.watchOptions) {
-      this.options.watchOptions = {};
-    }
-
     this.watchOptions = options.watchOptions || {};
 
     // Replace leading and trailing slashes to normalize path
diff --git a/lib/utils/normalizeOptions.js b/lib/utils/normalizeOptions.js
new file mode 100644
index 0000000000..443d2df94a
--- /dev/null
+++ b/lib/utils/normalizeOptions.js
@@ -0,0 +1,27 @@
+'use strict';
+
+/* eslint-disable
+  no-undefined
+*/
+
+function normalizeOptions(compiler, options) {
+  // Setup default value
+  options.contentBase =
+    options.contentBase !== undefined ? options.contentBase : process.cwd();
+
+  // set serverMode default
+  if (options.serverMode === undefined) {
+    options.serverMode = 'sockjs';
+  }
+
+  // set clientMode default
+  if (options.clientMode === undefined) {
+    options.clientMode = 'sockjs';
+  }
+
+  if (!options.watchOptions) {
+    options.watchOptions = {};
+  }
+}
+
+module.exports = normalizeOptions;
diff --git a/test/server/utils/__snapshots__/normalizeOptions.test.js.snap b/test/server/utils/__snapshots__/normalizeOptions.test.js.snap
new file mode 100644
index 0000000000..0658e08b4b
--- /dev/null
+++ b/test/server/utils/__snapshots__/normalizeOptions.test.js.snap
@@ -0,0 +1,40 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`normalizeOptions contentBase array should set correct options 1`] = `
+Object {
+  "clientMode": "sockjs",
+  "contentBase": Array [
+    "/path/to/dist1",
+    "/path/to/dist2",
+  ],
+  "serverMode": "sockjs",
+  "watchOptions": Object {},
+}
+`;
+
+exports[`normalizeOptions contentBase string should set correct options 1`] = `
+Object {
+  "clientMode": "sockjs",
+  "contentBase": "/path/to/dist",
+  "serverMode": "sockjs",
+  "watchOptions": Object {},
+}
+`;
+
+exports[`normalizeOptions no options should set correct options 1`] = `
+Object {
+  "clientMode": "sockjs",
+  "serverMode": "sockjs",
+  "watchOptions": Object {},
+}
+`;
+
+exports[`normalizeOptions watchOptions should set correct options 1`] = `
+Object {
+  "clientMode": "sockjs",
+  "serverMode": "sockjs",
+  "watchOptions": Object {
+    "poll": true,
+  },
+}
+`;
diff --git a/test/server/utils/normalizeOptions.test.js b/test/server/utils/normalizeOptions.test.js
new file mode 100644
index 0000000000..c1f66f4939
--- /dev/null
+++ b/test/server/utils/normalizeOptions.test.js
@@ -0,0 +1,73 @@
+'use strict';
+
+const webpack = require('webpack');
+const normalizeOptions = require('../../../lib/utils/normalizeOptions');
+
+describe('normalizeOptions', () => {
+  const cases = [
+    {
+      title: 'no options',
+      multiCompiler: false,
+      options: {},
+      optionsResults: null,
+    },
+    {
+      title: 'contentBase string',
+      multiCompiler: false,
+      options: {
+        contentBase: '/path/to/dist',
+      },
+      optionsResults: null,
+    },
+    {
+      title: 'contentBase array',
+      multiCompiler: false,
+      options: {
+        contentBase: ['/path/to/dist1', '/path/to/dist2'],
+      },
+      optionsResults: null,
+    },
+    {
+      title: 'watchOptions',
+      multiCompiler: false,
+      options: {
+        watchOptions: {
+          poll: true,
+        },
+      },
+      optionsResults: null,
+    },
+  ];
+
+  cases.forEach((data) => {
+    describe(data.title, () => {
+      let compiler;
+      beforeAll(() => {
+        let webpackConfig;
+        if (data.multiCompiler) {
+          webpackConfig = require('../../fixtures/multi-compiler-config/webpack.config');
+        } else {
+          webpackConfig = require('../../fixtures/simple-config/webpack.config');
+        }
+
+        compiler = webpack(webpackConfig);
+      });
+
+      it('should set correct options', () => {
+        const originalContentBase = data.options.contentBase;
+        normalizeOptions(compiler, data.options);
+        if (data.optionsResults) {
+          expect(data.options).toEqual(data.optionsResults);
+        } else {
+          if (data.options.contentBase !== originalContentBase) {
+            // we don't want this in the snapshot, because it is
+            // the current working directory
+            expect(data.options.contentBase).toEqual(process.cwd());
+            delete data.options.contentBase;
+          }
+          expect(data.options).toMatchSnapshot();
+        }
+      });
+    });
+  });
+});