diff --git a/README.md b/README.md
index d196c3d..13f2644 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,8 @@ npm i -s https-localhost
 ```
 Then put in your `index.js` file:
 ```
-const app = require("https-localhost")
+const httpsLocalhost = require("https-localhost")
+const app = httpLocalhost()
 // app is an express app, do what you usually do with express
 app.listen(port)
 ```
diff --git a/index.js b/index.js
index 4792197..d5fb907 100755
--- a/index.js
+++ b/index.js
@@ -24,55 +24,61 @@ try {
   process.exit(1)
 }
 
-// create a server with express
-const app = express()
+const createServer = () => {
+  // create a server with express
+  const app = express()
 
-// override the default express listen method to use our server
-app.listen = function(port = process.env.PORT ||
-/* istanbul ignore next: cannot be tested on Travis */ 443) {
-  app.server = https.createServer(certOptions, app).listen(port)
-  console.info("Server running on port " + port + ".")
-  return app.server
-}
+  // override the default express listen method to use our server
+  app.listen = function(port = process.env.PORT ||
+  /* istanbul ignore next: cannot be tested on Travis */ 443) {
+    app.server = https.createServer(certOptions, app).listen(port)
+    console.info("Server running on port " + port + ".")
+    return app.server
+  }
 
-// use gzip compression minify
-if (process.env.NODE_ENV === "production") {
-  app.use(compression({ threshold: 1 }))
-  app.use(minify())
-  app.set("json spaces", 0)
-}
+  // use gzip compression minify
+  if (process.env.NODE_ENV === "production") {
+    app.use(compression({ threshold: 1 }))
+    app.use(minify())
+    app.set("json spaces", 0)
+  }
 
-/* SETUP USEFUL FUNCTIONS */
+  /* SETUP USEFUL FUNCTIONS */
 
-// redirect http to https, usage `app.redirect()`
-app.redirect = function(
-/* istanbul ignore next: cannot be tested on Travis */ port = 80) {
-  app.http = http.createServer((req, res) => {
-    res.writeHead(301, { Location: "https://" + req.headers["host"] + req.url })
-    res.end()
-  }).listen(port)
-  console.info("http to https redirection active.")
-}
+  // redirect http to https, usage `app.redirect()`
+  app.redirect = function(
+  /* istanbul ignore next: cannot be tested on Travis */ port = 80) {
+    app.http = http.createServer((req, res) => {
+      res.writeHead(301, {
+        Location: "https://" + req.headers["host"] + req.url
+      })
+      res.end()
+    }).listen(port)
+    console.info("http to https redirection active.")
+  }
+
+  // serve static content, usage `app.serve([path])`
+  app.serve = function(staticPath = process.cwd(), port = process.env.PORT ||
+  /* istanbul ignore next: cannot be tested on Travis */ 443) {
+    app.use(express.static(staticPath))
+    // redirect 404 to 404.html or to index.html
+    app.use((req, res) => {
+      if (!staticPath.startsWith("/"))
+        staticPath = process.cwd() + "/" + staticPath
+      const p404 = staticPath + "/404.html"
+      const index = staticPath + "/index.html"
+      // istanbul ignore else: not interesting
+      if (fs.existsSync(p404))
+        res.status(404).sendFile(p404)
+      else if (fs.existsSync(index))
+        res.status(404).sendFile(index)
+      else res.status(404).send(req.path + " not found.")
+    })
+    console.info("Serving static path: " + staticPath)
+    app.listen(port)
+  }
 
-// serve static content, usage `app.serve([path])`
-app.serve = function(staticPath = process.cwd(), port = process.env.PORT ||
-/* istanbul ignore next: cannot be tested on Travis */ 443) {
-  app.use(express.static(staticPath))
-  // redirect 404 to 404.html or to index.html
-  app.use((req, res) => {
-    if (!staticPath.startsWith("/"))
-      staticPath = process.cwd() + "/" + staticPath
-    const p404 = staticPath + "/404.html"
-    const index = staticPath + "/index.html"
-    // istanbul ignore else: not interesting
-    if (fs.existsSync(p404))
-      res.status(404).sendFile(p404)
-    else if (fs.existsSync(index))
-      res.status(404).sendFile(index)
-    else res.status(404).send(req.path + " not found.")
-  })
-  console.info("Serving static path: " + staticPath)
-  app.listen(port)
+  return app
 }
 
 /* MAIN */
@@ -80,6 +86,7 @@ app.serve = function(staticPath = process.cwd(), port = process.env.PORT ||
 // usage: `serve [<path>]` or `node index.js [<path>]`
 // istanbul ignore if: cannot be tested
 if (require.main === module) {
+  const app = createServer()
   // retrieve the static path from the process argv or use the cwd
   // 1st is node, 2nd is serve or index.js, 3rd (if exists) is the path
   app.serve(process.argv.length === 3 ? process.argv[2] : process.cwd())
@@ -88,4 +95,4 @@ if (require.main === module) {
 }
 
 // export as module
-module.exports = app
+module.exports = createServer
diff --git a/test/test.js b/test/test.js
index b9a09d1..f6e3fab 100644
--- a/test/test.js
+++ b/test/test.js
@@ -3,7 +3,7 @@ const fs = require("fs")
 const http = require("http")
 const https = require("https")
 
-const app = require("../index.js")
+const app = require("../index.js")()
 
 const HTTPS_PORT = 4443
 const HTTP_PORT = 8080
@@ -125,7 +125,7 @@ describe("Testing https-localhost", () => {
     // set NODE_ENV to production
     delete require.cache[require.resolve("../index.js")]
     process.env.NODE_ENV = "production"
-    const production = require("../index.js")
+    const production = require("../index.js")()
     // start the server (serving the test folder)
     production.serve("test", HTTPS_PORT)
     // make the request and check the output