diff --git a/lib/clients.js b/lib/clients.js
index a66defe..2d9e7aa 100644
--- a/lib/clients.js
+++ b/lib/clients.js
@@ -4,17 +4,17 @@ let url = require('url')
 
 function insecureURL (uri) {
   if (uri.protocol === 'https:') return false
-  // allow localhost, 10.* and 192.* clients for testing
-  if (uri.host === 'localhost') return false
-  if (/\.local$/.test(uri.host)) return false
-  if (uri.host.match(/^(10\.|192\.)/)) return false
+  // allow non-https localhost, 10.*, 127.*, and 192.* clients for testing
+  if (/^localhost(?:[:]\d+)?$/.test(uri.host)) return false
+  if (/\.local(?:[:]\d+)?$/.test(uri.host)) return false
+  if (uri.host.match(/^(10|127|192)\.\d{1,3}\.\d{1,3}\.\d{1,3}(?:[:]\d+)?$/)) return false
   return true
 }
 
 function validateURL (uri) {
   let u = url.parse(uri)
   if (!u.protocol) throw new Error('Invalid URL')
-  if (insecureURL(u)) throw new Error('Unsupported callback URL. Clients have to use HTTPS.')
+  if (insecureURL(u)) throw new Error('Unsupported callback URL. Clients have to use HTTPS for non-local addresses.')
   return uri
 }
 
diff --git a/test/clients.js b/test/clients.js
index 33fd57f..a57e15c 100644
--- a/test/clients.js
+++ b/test/clients.js
@@ -8,22 +8,38 @@ describe('clients', () => {
   describe('secure URLs', () => {
     [
       {uri: 'https://heroku.com'},
+      {uri: 'https://heroku.com:8080/foo'},
       {uri: 'http://localhost'},
+      {uri: 'http://localhost:8080/foo'},
       {uri: 'http://foo.local'},
+      {uri: 'http://foo.local/foo'},
       {uri: 'http://10.0.0.1'},
-      {uri: 'http://192.168.0.1'}
+      {uri: 'http://10.0.0.1:8080/foo'},
+      {uri: 'http://127.0.0.1'},
+      {uri: 'http://127.0.0.1:8080/foo'},
+      {uri: 'http://192.168.0.1'},
+      {uri: 'http://192.168.0.1:8080/foo'}
     ].forEach(test => {
-      it(test.uri, () => {
+      it('passes when secure (' + test.uri + ')', () => {
         clients.validateURL(test.uri)
       })
     })
+  })
 
-    it('fails when insecure', () => {
-      expect(() => clients.validateURL('http://heroku.com'), 'to error', 'Unsupported callback URL. Clients have to use HTTPS.')
+  describe('insecure URLs', () => {
+    [
+      {uri: 'http://heroku.com'},
+      {uri: 'http://10.foo.com'},
+      {uri: 'http://127.foo.com'},
+      {uri: 'http://192.foo.com'}
+    ].forEach(test => {
+      it('fails when insecure (' + test.uri + ')', () => {
+        expect(() => clients.validateURL(test.uri), 'to error', 'Unsupported callback URL. Clients have to use HTTPS for non-local addresses.')
+      })
     })
+  })
 
-    it('fails when invalid', () => {
-      expect(() => clients.validateURL('foo'), 'to error', 'Invalid URL')
-    })
+  it('fails when invalid', () => {
+    expect(() => clients.validateURL('foo'), 'to error', 'Invalid URL')
   })
 })