diff --git a/src/URI.js b/src/URI.js
index f63ad6c6..6f7fd572 100644
--- a/src/URI.js
+++ b/src/URI.js
@@ -240,16 +240,10 @@
     ws: '80',
     wss: '443'
   };
-  // list of protocols which always require a hostname
-  URI.hostProtocols = [
-    'http',
-    'https'
-  ];
-
   // allowed hostname characters according to RFC 3986
   // ALPHA DIGIT "-" "." "_" "~" "!" "$" "&" "'" "(" ")" "*" "+" "," ";" "=" %encoded
   // I've never seen a (non-IDN) hostname other than: ALPHA DIGIT . -
-  URI.invalid_hostname_characters = /[^a-zA-Z0-9\.\-:]/;
+  URI.invalid_hostname_characters = /[^a-zA-Z0-9\.-]/;
   // map DOM Elements to their URI attribute
   URI.domAttributes = {
     'a': 'href',
@@ -581,12 +575,6 @@
       string = '/' + string;
     }
 
-    URI.ensureValidHostname(parts.hostname, parts.protocol);
-
-    if (parts.port) {
-      URI.ensureValidPort(parts.port);
-    }
-
     return string.substring(pos) || '/';
   };
   URI.parseAuthority = function(string, parts) {
@@ -1027,44 +1015,22 @@
     return string;
   };
 
-  URI.ensureValidHostname = function(v, protocol) {
+  URI.ensureValidHostname = function(v) {
     // Theoretically URIs allow percent-encoding in Hostnames (according to RFC 3986)
     // they are not part of DNS and therefore ignored by URI.js
 
-    var hasHostname = !!v; // not null and not an empty string
-    var hasProtocol = !!protocol;
-    var rejectEmptyHostname = false;
-
-    if (hasProtocol) {
-      rejectEmptyHostname = arrayContains(URI.hostProtocols, protocol);
-    }
-
-    if (rejectEmptyHostname && !hasHostname) {
-      throw new TypeError('Hostname cannot be empty, if protocol is ' + protocol);
-    } else if (v && v.match(URI.invalid_hostname_characters)) {
+    if (v.match(URI.invalid_hostname_characters)) {
       // test punycode
       if (!punycode) {
         throw new TypeError('Hostname "' + v + '" contains characters other than [A-Z0-9.-] and Punycode.js is not available');
       }
+
       if (punycode.toASCII(v).match(URI.invalid_hostname_characters)) {
-        throw new TypeError('Hostname "' + v + '" contains characters other than [A-Z0-9.:-]');
+        throw new TypeError('Hostname "' + v + '" contains characters other than [A-Z0-9.-]');
       }
     }
   };
 
-  URI.ensureValidPort = function (v) {
-    if (!v) {
-      return;
-    }
-
-    var port = Number(v);
-    if (Number.isInteger(port) && (port > 0) && (port < 65536)) {
-      return;
-    }
-
-    throw new TypeError('Port "' + v + '" is not a valid port');
-  };
-
   // noConflict
   URI.noConflict = function(removeAll) {
     if (removeAll) {
@@ -1322,7 +1288,9 @@
           v = v.substring(1);
         }
 
-        URI.ensureValidPort(v);
+        if (v.match(/[^0-9]/)) {
+          throw new TypeError('Port "' + v + '" contains characters other than [0-9]');
+        }
       }
     }
     return _port.call(this, v, build);
@@ -1340,7 +1308,6 @@
       }
 
       v = x.hostname;
-      URI.ensureValidHostname(v, this._parts.protocol);
     }
     return _hostname.call(this, v, build);
   };
@@ -1459,12 +1426,8 @@
         v += '.';
       }
 
-      if (v.indexOf(':') !== -1) {
-        throw new TypeError('Domains cannot contain colons');
-      }
-
       if (v) {
-        URI.ensureValidHostname(v, this._parts.protocol);
+        URI.ensureValidHostname(v);
       }
 
       this._parts.hostname = this._parts.hostname.replace(replace, v);
@@ -1503,11 +1466,7 @@
         throw new TypeError('cannot set domain empty');
       }
 
-      if (v.indexOf(':') !== -1) {
-        throw new TypeError('Domains cannot contain colons');
-      }
-
-      URI.ensureValidHostname(v, this._parts.protocol);
+      URI.ensureValidHostname(v);
 
       if (!this._parts.hostname || this.is('IP')) {
         this._parts.hostname = v;
diff --git a/test/test.js b/test/test.js
index 8ebf8623..1cc2ce5d 100644
--- a/test/test.js
+++ b/test/test.js
@@ -124,26 +124,6 @@
     ok(u instanceof URI, 'instanceof URI');
     ok(u._parts.hostname !== undefined, 'host undefined');
   });
-  test('function URI(string) with invalid port "port" throws', function () {
-    raises(function () {
-      new URI('http://example.org:port');
-    }, TypeError, "throws TypeError");
-  });
-  test('function URI(string) with invalid port "0" throws', function () {
-    raises(function () {
-      new URI('http://example.org:0');
-    }, TypeError, "throws TypeError");
-  });
-  test('function URI(string) with invalid port "65536" throws', function () {
-    raises(function () {
-      new URI('http://example.org:65536');
-    }, TypeError, "throws TypeError");
-  });
-  test('function URI(string) with protocol and without hostname should throw', function () {
-    raises(function () {
-      new URI('http://');
-    }, TypeError, "throws TypeError");
-  });
   test('new URI(string, string)', function() {
     // see http://dvcs.w3.org/hg/url/raw-file/tip/Overview.html#constructor
     var u = new URI('../foobar.html', 'http://example.org/hello/world.html');
@@ -243,16 +223,13 @@
     equal(u.hostname(), 'abc.foobar.lala', 'hostname changed');
     equal(u+'', 'http://abc.foobar.lala/foo.html', 'hostname changed url');
 
+    u.hostname('');
+    equal(u.hostname(), '', 'hostname removed');
+    equal(u+'', 'http:///foo.html', 'hostname removed url');
+
     raises(function() {
       u.hostname('foo\\bar.com');
     }, TypeError, 'Failing backslash detection in hostname');
-
-    raises(function() {
-      u.hostname('');
-    }, TypeError, "Trying to set an empty hostname with http(s) protocol throws a TypeError");
-    raises(function() {
-      u.hostname(null);
-    }, TypeError, "Trying to set hostname to null with http(s) protocol throws a TypeError");
   });
   test('port', function() {
     var u = new URI('http://example.org/foo.html');
@@ -1361,6 +1338,11 @@
         url: 'file:///C:/skyclan/snipkit',
         base: 'http://example.com/foo/bar',
         result: 'file:///C:/skyclan/snipkit'
+      }, {
+        name: 'absolute passthru - generic empty-hostname - urljoin (#328)',
+        url: 'http:///foo',
+        base: 'http://example.com/foo/bar',
+        result: 'http:///foo'
       }, {
         name: 'file paths - urljoin',
         url: 'anotherFile',