diff --git a/Curl.php b/Curl.php
index d33efed..e777fc8 100644
--- a/Curl.php
+++ b/Curl.php
@@ -80,6 +80,7 @@ public function __construct(array $options = array(), $followLocationMaxRedirect
         if (isset($options['connection_timeout'])) {
             curl_setopt($this->ch, CURLOPT_CONNECTTIMEOUT, $options['connection_timeout']);
         }
+
         if (isset($options['proxy_host'])) {
             if (false !== $options['proxy_host']) {
                 $proxyHost = $options['proxy_host'].(isset($options['proxy_port']) ? $options['proxy_port'] : 8080);
@@ -88,10 +89,16 @@ public function __construct(array $options = array(), $followLocationMaxRedirect
             }
 
             curl_setopt($this->ch, CURLOPT_PROXY, $proxyHost);
+
+            if (false !== $proxyHost && isset($options['proxy_login'])) {
+                curl_setopt($this->ch, CURLOPT_PROXYUSERPWD, $options['proxy_login'].':'.$options['proxy_password']);
+
+                if (isset($options['proxy_auth'])) {
+                    curl_setopt($this->ch, CURLOPT_PROXYAUTH, $options['proxy_auth']);
+                }
+            }
         }
-        if (isset($options['proxy_user'])) {
-            curl_setopt($this->ch, CURLOPT_PROXYUSERPWD, $options['proxy_user'] . ':' . $options['proxy_password']);
-        }
+
         if (isset($options['login'])) {
             curl_setopt($this->ch, CURLOPT_HTTPAUTH, isset($options['extra_options']['http_auth']) ? $options['extra_options']['http_auth'] : CURLAUTH_ANY);
             curl_setopt($this->ch, CURLOPT_USERPWD, $options['login'].':'.$options['password']);
diff --git a/SoapClientBuilder.php b/SoapClientBuilder.php
index cce4a9a..59b5bba 100644
--- a/SoapClientBuilder.php
+++ b/SoapClientBuilder.php
@@ -175,19 +175,28 @@ public function withDigestAuthentication($certificate, $passphrase = null)
      *
      * @param string $host     Host
      * @param int    $port     Port
-     * @param string $username Username
+     * @param string $login    Login
      * @param string $password Password
+     * @param int    $auth     Authentication method
      *
      * @return \BeSimple\SoapClient\SoapClientBuilder
      */
-    public function withProxy($host, $port, $username = null, $password = null)
+    public function withProxy($host, $port, $login = null, $password = null, $auth = null)
     {
         $this->soapOptions['proxy_host'] = $host;
         $this->soapOptions['proxy_port'] = $port;
 
-        if ($username) {
-            $this->soapOptions['proxy_login']    = $username;
+        if ($login) {
+            $this->soapOptions['proxy_login'] = $login;
             $this->soapOptions['proxy_password'] = $password;
+
+            if ($auth) {
+                if (!in_array($auth, array(\CURLAUTH_BASIC, \CURLAUTH_NTLM), true)) {
+                    throw new \InvalidArgumentException('Invalid authentication method: CURLAUTH_BASIC or CURLAUTH_NTLM constants are availables.');
+                }
+
+                $this->soapOptions['proxy_auth'] = $auth;
+            }
         }
 
         return $this;
@@ -236,4 +245,4 @@ protected function validateOptions()
     {
         $this->validateWsdl();
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/AxisInterop/MtomAxisInteropTest.php b/Tests/AxisInterop/MtomAxisInteropTest.php
index 27d9e20..f16f8c4 100644
--- a/Tests/AxisInterop/MtomAxisInteropTest.php
+++ b/Tests/AxisInterop/MtomAxisInteropTest.php
@@ -28,6 +28,7 @@ class MtomAxisInteropTest extends TestCase
             'base64Binary'      => 'BeSimple\SoapClient\Tests\AxisInterop\Fixtures\base64Binary',
             'AttachmentRequest' => 'BeSimple\SoapClient\Tests\AxisInterop\Fixtures\AttachmentRequest',
         ),
+        'proxy_host' => false,
     );
 
     public function testAttachment()
@@ -48,4 +49,4 @@ public function testAttachment()
 //         $this->assertEquals($b64->_, file_get_contents($fileCreatedByServer));
 //         unlink($fileCreatedByServer);
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/AxisInterop/SwaAxisInteropTest.php b/Tests/AxisInterop/SwaAxisInteropTest.php
index 4b9921f..d964aa3 100644
--- a/Tests/AxisInterop/SwaAxisInteropTest.php
+++ b/Tests/AxisInterop/SwaAxisInteropTest.php
@@ -37,6 +37,7 @@ class SwaAxisInteropTest extends TestCase
             'uploadFile'           => 'BeSimple\SoapClient\Tests\AxisInterop\Fixtures\uploadFile',
             'uploadFileResponse'   => 'BeSimple\SoapClient\Tests\AxisInterop\Fixtures\uploadFileResponse',
         ),
+        'proxy_host' => false,
     );
 
     public function testUploadDownloadText()
@@ -74,4 +75,4 @@ public function testUploadDownloadImage()
 
         $this->assertEquals($upload->data, $result->data);
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/AxisInterop/WsAddressingAxisInteropTest.php b/Tests/AxisInterop/WsAddressingAxisInteropTest.php
index cf7308a..2310476 100644
--- a/Tests/AxisInterop/WsAddressingAxisInteropTest.php
+++ b/Tests/AxisInterop/WsAddressingAxisInteropTest.php
@@ -32,6 +32,7 @@ class WsAddressingAxisInteropTest extends TestCase
     private $options = array(
         'soap_version' => SOAP_1_2,
         'features'     => SOAP_SINGLE_ELEMENT_ARRAYS, // make sure that result is array for size=1
+        'proxy_host' => false,
     );
 
     public function testSession()
@@ -56,4 +57,4 @@ public function testSession()
 
         $this->assertEquals($soapSessionId1, $soapSessionId2);
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/AxisInterop/WsSecuritySigEncAxisInteropTest.php b/Tests/AxisInterop/WsSecuritySigEncAxisInteropTest.php
index 6e4f0d9..2d7070e 100644
--- a/Tests/AxisInterop/WsSecuritySigEncAxisInteropTest.php
+++ b/Tests/AxisInterop/WsSecuritySigEncAxisInteropTest.php
@@ -64,6 +64,7 @@ class WsSecuritySigEncAxisInteropTest extends TestCase
             'addBookResponse'        => 'BeSimple\SoapClient\Tests\AxisInterop\Fixtures\addBookResponse',
             'BookInformation'        => 'BeSimple\SoapClient\Tests\AxisInterop\Fixtures\BookInformation',
         ),
+        'proxy_host' => false,
     );
 
     public function testSigEnc()
@@ -103,4 +104,4 @@ public function testSigEnc()
 
         // getBooksByType("scifi");
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/AxisInterop/WsSecurityUserPassAxisInteropTest.php b/Tests/AxisInterop/WsSecurityUserPassAxisInteropTest.php
index 6ab2824..2ee71d6 100644
--- a/Tests/AxisInterop/WsSecurityUserPassAxisInteropTest.php
+++ b/Tests/AxisInterop/WsSecurityUserPassAxisInteropTest.php
@@ -40,6 +40,7 @@ class WsSecurityUserPassAxisInteropTest extends TestCase
             'addBookResponse'        => 'BeSimple\SoapClient\Tests\AxisInterop\Fixtures\addBookResponse',
             'BookInformation'        => 'BeSimple\SoapClient\Tests\AxisInterop\Fixtures\BookInformation',
         ),
+        'proxy_host' => false,
     );
 
     public function testUserPassText()
@@ -93,4 +94,4 @@ public function testUserPassDigest()
 
         // getBooksByType("scifi");
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/CurlTest.php b/Tests/CurlTest.php
index c80b992..28b6311 100644
--- a/Tests/CurlTest.php
+++ b/Tests/CurlTest.php
@@ -74,7 +74,9 @@ public function testGetResponse()
 
     public function testGetResponseBody()
     {
-        $curl = new Curl();
+        $curl = new Curl(array(
+            'proxy_host' => false,
+        ));
 
         $curl->exec(sprintf('http://localhost:%d/curl.txt', WEBSERVER_PORT));
         $this->assertEquals('This is a testfile for cURL.', $curl->getResponseBody());
@@ -82,7 +84,9 @@ public function testGetResponseBody()
 
     public function testGetResponseContentType()
     {
-        $curl = new Curl();
+        $curl = new Curl(array(
+            'proxy_host' => false,
+        ));
 
         $curl->exec(sprintf('http://localhost:%d/curl.txt', WEBSERVER_PORT));
         $this->assertEquals('text/plain; charset=UTF-8', $curl->getResponseContentType());
@@ -93,7 +97,9 @@ public function testGetResponseContentType()
 
     public function testGetResponseHeaders()
     {
-        $curl = new Curl();
+        $curl = new Curl(array(
+            'proxy_host' => false,
+        ));
 
         $curl->exec(sprintf('http://localhost:%d/curl.txt', WEBSERVER_PORT));
         $this->assertEquals(117 + self::$websererPortLength, strlen($curl->getResponseHeaders()));
@@ -104,7 +110,9 @@ public function testGetResponseHeaders()
 
     public function testGetResponseStatusCode()
     {
-        $curl = new Curl();
+        $curl = new Curl(array(
+            'proxy_host' => false,
+        ));
 
         $curl->exec(sprintf('http://localhost:%d/curl.txt', WEBSERVER_PORT));
         $this->assertEquals(200, $curl->getResponseStatusCode());
diff --git a/Tests/ServerInterop/MtomServerInteropTest.php b/Tests/ServerInterop/MtomServerInteropTest.php
index 779313f..07d7b48 100644
--- a/Tests/ServerInterop/MtomServerInteropTest.php
+++ b/Tests/ServerInterop/MtomServerInteropTest.php
@@ -20,6 +20,7 @@ class MtomServerInteropTest extends TestCase
             'base64Binary'      => 'BeSimple\SoapClient\Tests\ServerInterop\Fixtures\base64Binary',
             'AttachmentRequest' => 'BeSimple\SoapClient\Tests\ServerInterop\Fixtures\AttachmentRequest',
         ),
+        'proxy_host' => false,
     );
 
     public function testAttachment()
@@ -40,4 +41,4 @@ public function testAttachment()
         $this->assertEquals($b64->_, file_get_contents($fileCreatedByServer));
         unlink($fileCreatedByServer);
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/ServerInterop/SwaServerInteropTest.php b/Tests/ServerInterop/SwaServerInteropTest.php
index 5f3e6f3..01eaeae 100644
--- a/Tests/ServerInterop/SwaServerInteropTest.php
+++ b/Tests/ServerInterop/SwaServerInteropTest.php
@@ -23,6 +23,7 @@ class SwaServerInteropTest extends TestCase
             'uploadFile'           => 'BeSimple\SoapClient\Tests\ServerInterop\Fixtures\uploadFile',
             'uploadFileResponse'   => 'BeSimple\SoapClient\Tests\ServerInterop\Fixtures\uploadFileResponse',
         ),
+        'proxy_host' => false,
     );
 
     public function testUploadDownloadText()
diff --git a/Tests/ServerInterop/WsSecuritySigEncServerInteropTest.php b/Tests/ServerInterop/WsSecuritySigEncServerInteropTest.php
index 0ff0142..8978fd6 100644
--- a/Tests/ServerInterop/WsSecuritySigEncServerInteropTest.php
+++ b/Tests/ServerInterop/WsSecuritySigEncServerInteropTest.php
@@ -30,6 +30,7 @@ class WsSecuritySigEncServerInteropTest extends TestCase
             'addBookResponse'        => 'BeSimple\SoapClient\Tests\ServerInterop\Fixtures\addBookResponse',
             'BookInformation'        => 'BeSimple\SoapClient\Tests\ServerInterop\Fixtures\BookInformation',
         ),
+        'proxy_host' => false,
     );
 
     public function testSigEnc()
@@ -69,4 +70,4 @@ public function testSigEnc()
 
         // getBooksByType("scifi");
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/ServerInterop/WsSecurityUserPassServerInteropTest.php b/Tests/ServerInterop/WsSecurityUserPassServerInteropTest.php
index 1df839c..efe86b5 100644
--- a/Tests/ServerInterop/WsSecurityUserPassServerInteropTest.php
+++ b/Tests/ServerInterop/WsSecurityUserPassServerInteropTest.php
@@ -29,6 +29,7 @@ class WsSecurityUserPassServerInteropTest extends TestCase
             'addBookResponse'        => 'BeSimple\SoapClient\Tests\ServerInterop\Fixtures\addBookResponse',
             'BookInformation'        => 'BeSimple\SoapClient\Tests\ServerInterop\Fixtures\BookInformation',
         ),
+        'proxy_host' => false,
     );
 
     public function testUserPassText()
@@ -82,4 +83,4 @@ public function testUserPassDigest()
 
         // getBooksByType("scifi");
     }
-}
\ No newline at end of file
+}
diff --git a/Tests/SoapClientBuilderTest.php b/Tests/SoapClientBuilderTest.php
index a0ebfeb..e9aecfb 100644
--- a/Tests/SoapClientBuilderTest.php
+++ b/Tests/SoapClientBuilderTest.php
@@ -96,6 +96,20 @@ public function testWithProxy()
 
         $builder->withProxy('127.0.0.1', 8585, 'foo', 'bar');
         $this->assertEquals($this->mergeOptions(array('proxy_host' => '127.0.0.1', 'proxy_port' => 8585, 'proxy_login' => 'foo', 'proxy_password' => 'bar')), $builder->getSoapOptions());
+
+        $builder->withProxy('127.0.0.1', 8585, 'foo', 'bar', \CURLAUTH_BASIC);
+        $this->assertEquals($this->mergeOptions(array('proxy_host' => '127.0.0.1', 'proxy_port' => 8585, 'proxy_login' => 'foo', 'proxy_password' => 'bar', 'proxy_auth' => \CURLAUTH_BASIC)), $builder->getSoapOptions());
+
+        $builder->withProxy('127.0.0.1', 8585, 'foo', 'bar', \CURLAUTH_NTLM);
+        $this->assertEquals($this->mergeOptions(array('proxy_host' => '127.0.0.1', 'proxy_port' => 8585, 'proxy_login' => 'foo', 'proxy_password' => 'bar', 'proxy_auth' => \CURLAUTH_NTLM)), $builder->getSoapOptions());
+
+        try {
+            $builder->withProxy('127.0.0.1', 8585, 'foo', 'bar', -100);
+
+            $this->fail('An expected exception has not been raised.');
+        } catch (\Exception $e) {
+            $this->assertInstanceOf('InvalidArgumentException', $e);
+        }
     }
 
     public function testCreateWithDefaults()
diff --git a/Tests/WsdlDownloaderTest.php b/Tests/WsdlDownloaderTest.php
index 9597ca6..a5e4595 100644
--- a/Tests/WsdlDownloaderTest.php
+++ b/Tests/WsdlDownloaderTest.php
@@ -115,7 +115,9 @@ public function testResolveWsdlIncludes($source, $cacheFile, $remoteParentUrl, $
         Cache::setDirectory($wsdlCacheUrl);
         $cacheDirForRegExp = preg_quote($wsdlCacheUrl, '#');
 
-        $wsdlDownloader = new WsdlDownloader(new Curl());
+        $wsdlDownloader = new WsdlDownloader(new Curl(array(
+            'proxy_host' => false,
+        )));
         $r = new \ReflectionClass($wsdlDownloader);
         $m = $r->getMethod('resolveRemoteIncludes');
         $m->setAccessible(true);
@@ -178,7 +180,9 @@ public function testResolveXsdIncludes($source, $cacheFile, $remoteParentUrl, $r
         Cache::setDirectory($wsdlCacheUrl);
         $cacheDirForRegExp = preg_quote($wsdlCacheUrl, '#');
 
-        $wsdlDownloader = new WsdlDownloader(new Curl());
+        $wsdlDownloader = new WsdlDownloader(new Curl(array(
+            'proxy_host' => false,
+        )));
         $r = new \ReflectionClass($wsdlDownloader);
         $m = $r->getMethod('resolveRemoteIncludes');
         $m->setAccessible(true);