diff --git a/README.md b/README.md
index 810c098..b98ca36 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ $ composer require matejsvajger/ntlm-soap-client
 ``` php
 $url = 'URL_TO_WEBSERVICE_WSDL';
 $config = new matejsvajger\NTLMSoap\Common\NTLMConfig([
-    'domain'   => 'domain',
+    'domain'   => 'domain',    // Can be omitted
     'username' => 'username',
     'password' => 'password'
 ]);
@@ -32,7 +32,7 @@ foreach ($response->ReadMultiple_Result->CRMContactlist as $entity) {
     print_r($entity);
 }
 ```
-__NOTE:__ NTLM Authentication string looks like `<domain>/<username>:<password>`. _All three config items are required._
+__NOTE:__ NTLM Authentication string can look like `<domain>/<username>:<password>` or `<username>:<password>`. _`<username>` and `<password>` config items are required._
 
 ## Change log
 
diff --git a/composer.json b/composer.json
index f170302..235ae67 100644
--- a/composer.json
+++ b/composer.json
@@ -17,8 +17,8 @@
         }
     ],
     "require": {
-        "php": "~5.6|~7.0",
-        "symfony/console": "^3.1"
+        "php": "~5.6|~7.0|~8.0",
+        "symfony/console": "^3.1||^4.0||^5.0||^6.0"
     },
     "require-dev": {
         "phpunit/phpunit" : "~4.0||~5.0",
diff --git a/src/NTLMSoap/Common/NTLMConfig.php b/src/NTLMSoap/Common/NTLMConfig.php
index 62b148a..ea349d1 100644
--- a/src/NTLMSoap/Common/NTLMConfig.php
+++ b/src/NTLMSoap/Common/NTLMConfig.php
@@ -9,7 +9,7 @@ class NTLMConfig implements \Serializable, \Iterator
     private $parameters = [];
 
     protected $requiredParameters = [
-        'domain', 'username', 'password'
+        'username', 'password'
     ];
 
     public function __construct(array $config)
@@ -24,7 +24,7 @@ public function __construct(array $config)
     }
 
     /**
-     * Returns a "<domain>/<username>:<password>" formated
+     * Returns a "<domain>/<username>:<password>" or "<username>:<password>" formatted
      * string, required for NTLM Authentication headers.
      *
      * @author Matej Svajger <matej.svajger@koerbler.com>
@@ -35,11 +35,11 @@ public function __construct(array $config)
      */
     public static function getAuthString()
     {
-        $domain   = $GLOBALS['NTLMClientDomain'];
+        $domain   = isset($GLOBALS['NTLMClientDomain']) && !empty($GLOBALS['NTLMClientDomain']) ? $GLOBALS['NTLMClientDomain'] : '';
         $username = $GLOBALS['NTLMClientUsername'];
         $password = $GLOBALS['NTLMClientPassword'];
 
-        return "{$domain}/{$username}:{$password}";
+        return sprintf('%s%s:%s', $domain ? $domain.'/' : '', $username, $password);
     }
 
     /**
@@ -61,6 +61,11 @@ protected function assertParametersAreValid(array $parameters)
         }
     }
 
+    public function __isset($param)
+    {
+        return isset($this->parameters[$param]);
+    }
+
     public function __set($param, $value)
     {
         $this->parameters[$param] = $value;