diff --git a/lib/http.js b/lib/http.js
index 7c6d753f..c67c3563 100644
--- a/lib/http.js
+++ b/lib/http.js
@@ -440,8 +440,15 @@ function Server(options) {
   var start = this._start.bind(this);
   var fallback = this._fallback.bind(this);
 
+  // HTTP2 over plain TCP
+  if (options.plain) {
+    this._log.info('Creating HTTP/2 server over plain TCP');
+    this._mode = 'plain';
+    this._server = net.createServer(start);
+  }
+
   // HTTP2 over TLS (using NPN or ALPN)
-  if ((options.key && options.cert) || options.pfx) {
+  else {
     this._log.info('Creating HTTP/2 server over TLS');
     this._mode = 'tls';
     options.ALPNProtocols = supportedProtocols;
@@ -467,19 +474,6 @@ function Server(options) {
     forwardEvent('listening', this._server, this);
   }
 
-  // HTTP2 over plain TCP
-  else if (options.plain) {
-    this._log.info('Creating HTTP/2 server over plain TCP');
-    this._mode = 'plain';
-    this._server = net.createServer(start);
-  }
-
-  // HTTP/2 with HTTP/1.1 upgrade
-  else {
-    this._log.error('Trying to create HTTP/2 server with Upgrade from HTTP/1.1');
-    throw new Error('HTTP1.1 -> HTTP2 upgrade is not yet supported. Please provide TLS keys.');
-  }
-
   this._server.on('close', this.emit.bind(this, 'close'));
 }
 Server.prototype = Object.create(EventEmitter.prototype, { constructor: { value: Server } });
@@ -611,10 +605,8 @@ function createServerRaw(options, requestListener) {
 
 function createServerTLS(options, requestListener) {
   if (typeof options === 'function') {
-    throw new Error('options are required!');
-  }
-  if (!options.pfx && !(options.key && options.cert)) {
-    throw new Error('options.pfx or options.key and options.cert are required!');
+    requestListener = options;
+    options = {};
   }
   options.plain = false;
 
diff --git a/test/http.js b/test/http.js
index efd0f393..fc054748 100644
--- a/test/http.js
+++ b/test/http.js
@@ -30,13 +30,13 @@ describe('http.js', function() {
   });
   describe('Server', function() {
     describe('new Server(options)', function() {
-      it('should throw if called without \'plain\' or TLS options', function() {
+      it('should not throw if called without \'plain\' or TLS options', function() {
         expect(function() {
-          new http2.Server();
-        }).to.throw(Error);
+          new http2.Server().close();
+        }).not.to.throw(Error);
         expect(function() {
-          http2.createServer(util.noop);
-        }).to.throw(Error);
+          http2.createServer(util.noop).close();
+        }).not.to.throw(Error);
       });
     });
     describe('method `listen()`', function () {