diff --git a/lib/Server.js b/lib/Server.js
index 11e5f67d3d..de8f299859 100644
--- a/lib/Server.js
+++ b/lib/Server.js
@@ -570,8 +570,21 @@ class Server {
         const value = options.https[property];
         const isBuffer = value instanceof Buffer;
 
-        if (value && !isBuffer && fs.lstatSync(value).isFile()) {
-          options.https[property] = fs.readFileSync(path.resolve(value));
+        if (value && !isBuffer) {
+          let stats = null;
+
+          try {
+            stats = fs.lstatSync(value).isFile();
+          } catch (error) {
+            // ignore error
+          }
+
+          if (stats) {
+            // It is file
+            options.https[property] = fs.readFileSync(path.resolve(value));
+          } else {
+            options.https[property] = value;
+          }
         }
       }
 
@@ -610,7 +623,7 @@ class Server {
           const pems = createCertificate(attrs);
 
           fs.writeFileSync(certPath, pems.private + pems.cert, {
-            encoding: 'utf-8',
+            encoding: 'utf8',
           });
         }
 
diff --git a/test/Https.test.js b/test/Https.test.js
index 676e0ad245..449a9f3a92 100644
--- a/test/Https.test.js
+++ b/test/Https.test.js
@@ -18,9 +18,8 @@ const contentBasePublic = path.join(
 describe('HTTPS', () => {
   let server;
   let req;
-  afterEach(helper.close);
 
-  describe('to directory', () => {
+  describe('is boolean', () => {
     beforeAll((done) => {
       server = helper.start(
         config,
@@ -36,6 +35,10 @@ describe('HTTPS', () => {
     it('Request to index', (done) => {
       req.get('/').expect(200, /Heyo/, done);
     });
+
+    afterAll(() => {
+      helper.close();
+    });
   });
 
   describe('ca, pfx, key and cert are buffer', () => {
@@ -68,7 +71,7 @@ describe('HTTPS', () => {
     });
   });
 
-  describe('ca, pfx, key and cert are string', () => {
+  describe('ca, pfx, key and cert are paths', () => {
     beforeAll((done) => {
       server = helper.start(
         config,
@@ -91,4 +94,39 @@ describe('HTTPS', () => {
       req.get('/').expect(200, /Heyo/, done);
     });
   });
+
+  describe('ca, pfx, key and cert are raw strings', () => {
+    beforeAll((done) => {
+      server = helper.start(
+        config,
+        {
+          contentBase: contentBasePublic,
+          https: {
+            ca: fs
+              .readFileSync(path.join(httpsCertificateDirectory, 'ca.pem'))
+              .toString(),
+            // pfx can't be string because it is binary format
+            pfx: fs.readFileSync(
+              path.join(httpsCertificateDirectory, 'server.pfx')
+            ),
+            key: fs
+              .readFileSync(path.join(httpsCertificateDirectory, 'server.key'))
+              .toString(),
+            cert: fs
+              .readFileSync(path.join(httpsCertificateDirectory, 'server.crt'))
+              .toString(),
+            passphrase: 'webpack-dev-server',
+          },
+        },
+        done
+      );
+      req = request(server.app);
+    });
+
+    it('Request to index', (done) => {
+      req.get('/').expect(200, /Heyo/, done);
+    });
+  });
+
+  afterEach(helper.close);
 });