diff --git a/index.js b/index.js
index 6482f77..5122dc1 100644
--- a/index.js
+++ b/index.js
@@ -1,4 +1,6 @@
 var crypto = require('crypto')
+  , url = require('url')
+  ;
 
 function sha (key, body, algorithm) {
   return crypto.createHmac(algorithm, key).update(body).digest('base64')
@@ -8,6 +10,17 @@ function rsa (key, body) {
   return crypto.createSign('RSA-SHA1').update(body).sign(key, 'base64')
 }
 
+function excludeDefaultPort (base_uri) {
+  var parsed = url.parse(base_uri);
+  if (parsed.port) {
+    if ((parsed.protocol == "http:" && parsed.port == "80")
+      || (parsed.protocol == "https:" && parsed.port == "443")) {
+      parsed.host = parsed.hostname;
+    }
+  }
+  return url.format(parsed);
+}
+
 function rfc3986 (str) {
   return encodeURIComponent(str)
     .replace(/!/g,'%21')
@@ -45,6 +58,10 @@ function generateBase (httpMethod, base_uri, params) {
   // adapted from https://dev.twitter.com/docs/auth/oauth and 
   // https://dev.twitter.com/docs/auth/creating-signature
 
+  // Exclude HTTPS for port 443, HTTP for port 80
+  // https://tools.ietf.org/html/rfc5849#section-3.4.1.2
+  var newBaseUri = excludeDefaultPort (base_uri)
+
   // Parameter normalization
   // http://tools.ietf.org/html/rfc5849#section-3.4.1.3.2
   var normalized = map(params)
@@ -69,7 +86,7 @@ function generateBase (httpMethod, base_uri, params) {
 
   var base = [
     rfc3986(httpMethod ? httpMethod.toUpperCase() : 'GET'),
-    rfc3986(base_uri),
+    rfc3986(newBaseUri),
     rfc3986(normalized)
   ].join('&')
 
diff --git a/test.js b/test.js
index 628515e..55983eb 100644
--- a/test.js
+++ b/test.js
@@ -105,11 +105,25 @@ var accsign = hmacsign('POST', 'https://api.twitter.com/oauth/access_token',
   , oauth_verifier: 'pDNg57prOHapMbhv25RNf75lVRd6JDsni1AJJIDYoTY'
   , oauth_version: '1.0'
   }, "MCD8BKwGdgPHvAuvgvz4EQpqDAtx89grbuNMRd7Eh98", "x6qpRnlEmW9JbQn4PQVVeVG8ZLPEx6A0TOebgwcuA")
-  
+
 console.log(accsign)
 console.log('PUw/dHA4fnlJYM6RhXk5IU/0fCc=')
 assert.equal(accsign, 'PUw/dHA4fnlJYM6RhXk5IU/0fCc=')
 
+var accsign2 = hmacsign('POST', 'https://api.twitter.com:443/oauth/access_token',
+{ oauth_consumer_key: 'GDdmIQH6jhtmLUypg82g'
+, oauth_nonce: '9zWH6qe0qG7Lc1telCn7FhUbLyVdjEaL3MO5uHxn8'
+, oauth_signature_method: 'HMAC-SHA1'
+, oauth_token: '8ldIZyxQeVrFZXFOZH5tAwj6vzJYuLQpl0WUEYtWc'
+, oauth_timestamp: '1272323047'
+, oauth_verifier: 'pDNg57prOHapMbhv25RNf75lVRd6JDsni1AJJIDYoTY'
+, oauth_version: '1.0'
+}, "MCD8BKwGdgPHvAuvgvz4EQpqDAtx89grbuNMRd7Eh98", "x6qpRnlEmW9JbQn4PQVVeVG8ZLPEx6A0TOebgwcuA")
+
+console.log(accsign2)
+console.log('PUw/dHA4fnlJYM6RhXk5IU/0fCc=')
+assert.equal(accsign2, 'PUw/dHA4fnlJYM6RhXk5IU/0fCc=')
+
 var upsign = hmacsign('POST', 'http://api.twitter.com/1/statuses/update.json', 
   { oauth_consumer_key: "GDdmIQH6jhtmLUypg82g"
   , oauth_nonce: "oElnnMTQIZvqvlfXM56aBLAf5noGD0AQR3Fmi7Q6Y"
@@ -124,6 +138,20 @@ console.log(upsign)
 console.log('yOahq5m0YjDDjfjxHaXEsW9D+X0=')
 assert.equal(upsign, 'yOahq5m0YjDDjfjxHaXEsW9D+X0=')
 
+var upsign2 = hmacsign('POST', 'http://api.twitter.com:80/1/statuses/update.json', 
+  { oauth_consumer_key: "GDdmIQH6jhtmLUypg82g"
+  , oauth_nonce: "oElnnMTQIZvqvlfXM56aBLAf5noGD0AQR3Fmi7Q6Y"
+  , oauth_signature_method: "HMAC-SHA1"
+  , oauth_token: "819797-Jxq8aYUDRmykzVKrgoLhXSq67TEa5ruc4GJC2rWimw"
+  , oauth_timestamp: "1272325550"
+  , oauth_version: "1.0"
+  , status: 'setting up my twitter 私のさえずりを設定する'
+  }, "MCD8BKwGdgPHvAuvgvz4EQpqDAtx89grbuNMRd7Eh98", "J6zix3FfA9LofH0awS24M3HcBYXO5nI1iYe8EfBA")
+
+console.log(upsign2)
+console.log('yOahq5m0YjDDjfjxHaXEsW9D+X0=')
+assert.equal(upsign2, 'yOahq5m0YjDDjfjxHaXEsW9D+X0=')
+
 // handle objects in params (useful for Wordpress REST API)
 var upsign = hmacsign('POST', 'http://wordpress.com/wp-json',
   { oauth_consumer_key: "GDdmIQH6jhtmLUypg82g"