diff --git a/README.md b/README.md
index daa9786..aa14ea1 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ https://github.com/SignRequest/signrequest-php-example
 
 ## Requirements
 
-PHP 5.5 and later
+PHP 7.1 and later
 
 ## Installation & Usage
 ### Composer
@@ -18,9 +18,21 @@ PHP 5.5 and later
 To install the bindings via [Composer](http://getcomposer.org/), add the following to `composer.json`:
 
 ```
+{
+    "repositories": {
+        "liquidline/signrequest-php-client": {
+            "type": "vcs",
+            "url": "https://github.com/liquidline/signrequest-php-client.git"
+        },
+    }
+}
+```  
+
+
+```     
 {
   "require": {
-    "signrequest/signrequest-client": "1.3.0"
+    "signrequest/signrequest-client": "1.4.2"
   }
 }
 ```
diff --git a/composer.json b/composer.json
index 1c81981..ff60d3c 100644
--- a/composer.json
+++ b/composer.json
@@ -1,6 +1,6 @@
 {
-    "name": "signrequest/signrequest-client",
-    "version": "1.3.0",
+    "name": "liquidline/signrequest-php-client",
+    "version": "1.4.2",
     "description": "Official PHP client for SignRequest.com (https://signrequest.com)",
     "keywords": [
         "signrequest",
@@ -17,11 +17,11 @@
         }
     ],
     "require": {
-        "php": ">=5.5",
+        "php": ">=7.1",
         "ext-curl": "*",
         "ext-json": "*",
         "ext-mbstring": "*",
-        "guzzlehttp/guzzle": "^6.2"
+        "guzzlehttp/guzzle": "^6.2|^7.0.1"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8",
@@ -34,4 +34,4 @@
     "autoload-dev": {
         "psr-4": { "SignRequest\\" : "test/" }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Api/ApiTokensApi.php b/src/Api/ApiTokensApi.php
index 58725d9..beafa67 100644
--- a/src/Api/ApiTokensApi.php
+++ b/src/Api/ApiTokensApi.php
@@ -328,7 +328,7 @@ protected function apiTokensListRequest($page = null, $limit = null)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -349,7 +349,7 @@ protected function apiTokensListRequest($page = null, $limit = null)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/DocumentAttachmentsApi.php b/src/Api/DocumentAttachmentsApi.php
index 9fc9882..efa0ef2 100644
--- a/src/Api/DocumentAttachmentsApi.php
+++ b/src/Api/DocumentAttachmentsApi.php
@@ -324,7 +324,7 @@ protected function documentAttachmentsCreateRequest($data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -345,7 +345,7 @@ protected function documentAttachmentsCreateRequest($data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -624,7 +624,7 @@ protected function documentAttachmentsListRequest($document__uuid = null, $docum
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -645,7 +645,7 @@ protected function documentAttachmentsListRequest($document__uuid = null, $docum
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -898,7 +898,7 @@ protected function documentAttachmentsReadRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -919,7 +919,7 @@ protected function documentAttachmentsReadRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/DocumentsApi.php b/src/Api/DocumentsApi.php
index 180804f..cf7ef64 100644
--- a/src/Api/DocumentsApi.php
+++ b/src/Api/DocumentsApi.php
@@ -68,9 +68,9 @@ class DocumentsApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -324,7 +324,7 @@ protected function documentsCreateRequest($data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -345,7 +345,7 @@ protected function documentsCreateRequest($data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -561,7 +561,7 @@ protected function documentsDeleteRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -582,7 +582,7 @@ protected function documentsDeleteRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'DELETE',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -915,7 +915,7 @@ protected function documentsListRequest($external_id = null, $signrequest__who =
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -936,7 +936,7 @@ protected function documentsListRequest($external_id = null, $signrequest__who =
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1189,7 +1189,7 @@ protected function documentsReadRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1210,7 +1210,7 @@ protected function documentsReadRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/DocumentsSearchApi.php b/src/Api/DocumentsSearchApi.php
index 811237e..673d3dd 100644
--- a/src/Api/DocumentsSearchApi.php
+++ b/src/Api/DocumentsSearchApi.php
@@ -68,9 +68,9 @@ class DocumentsSearchApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -409,7 +409,7 @@ protected function documentsSearchListRequest($page = null, $limit = null, $q =
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -430,7 +430,7 @@ protected function documentsSearchListRequest($page = null, $limit = null, $q =
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/EventsApi.php b/src/Api/EventsApi.php
index a59ff7f..24853e9 100644
--- a/src/Api/EventsApi.php
+++ b/src/Api/EventsApi.php
@@ -68,9 +68,9 @@ class EventsApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -445,7 +445,7 @@ protected function eventsListRequest($document__uuid = null, $document__external
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -466,7 +466,7 @@ protected function eventsListRequest($document__uuid = null, $document__external
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -719,7 +719,7 @@ protected function eventsReadRequest($id)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -740,7 +740,7 @@ protected function eventsReadRequest($id)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/SignrequestQuickCreateApi.php b/src/Api/SignrequestQuickCreateApi.php
index 56304a4..17fb790 100644
--- a/src/Api/SignrequestQuickCreateApi.php
+++ b/src/Api/SignrequestQuickCreateApi.php
@@ -68,9 +68,9 @@ class SignrequestQuickCreateApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -324,7 +324,7 @@ protected function signrequestQuickCreateCreateRequest($data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -345,7 +345,7 @@ protected function signrequestQuickCreateCreateRequest($data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/SignrequestsApi.php b/src/Api/SignrequestsApi.php
index 294735d..00b115b 100644
--- a/src/Api/SignrequestsApi.php
+++ b/src/Api/SignrequestsApi.php
@@ -68,9 +68,9 @@ class SignrequestsApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -329,7 +329,7 @@ protected function signrequestsCancelSignrequestRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -350,7 +350,7 @@ protected function signrequestsCancelSignrequestRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -598,7 +598,7 @@ protected function signrequestsCreateRequest($data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -619,7 +619,7 @@ protected function signrequestsCreateRequest($data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -889,7 +889,7 @@ protected function signrequestsListRequest($who = null, $from_email = null, $pag
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -910,7 +910,7 @@ protected function signrequestsListRequest($who = null, $from_email = null, $pag
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1163,7 +1163,7 @@ protected function signrequestsReadRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1184,7 +1184,7 @@ protected function signrequestsReadRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1437,7 +1437,7 @@ protected function signrequestsResendSignrequestEmailRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1458,7 +1458,7 @@ protected function signrequestsResendSignrequestEmailRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/TeamMembersApi.php b/src/Api/TeamMembersApi.php
index 3eda6ab..adb5b6a 100644
--- a/src/Api/TeamMembersApi.php
+++ b/src/Api/TeamMembersApi.php
@@ -68,9 +68,9 @@ class TeamMembersApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -382,7 +382,7 @@ protected function teamMembersListRequest($is_active = null, $is_owner = null, $
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -403,7 +403,7 @@ protected function teamMembersListRequest($is_active = null, $is_owner = null, $
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -656,7 +656,7 @@ protected function teamMembersReadRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -677,7 +677,7 @@ protected function teamMembersReadRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/TeamsApi.php b/src/Api/TeamsApi.php
index 0b2268a..9989734 100644
--- a/src/Api/TeamsApi.php
+++ b/src/Api/TeamsApi.php
@@ -68,9 +68,9 @@ class TeamsApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -324,7 +324,7 @@ protected function teamsCreateRequest($data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -345,7 +345,7 @@ protected function teamsCreateRequest($data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -561,7 +561,7 @@ protected function teamsDeleteRequest($subdomain)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -582,7 +582,7 @@ protected function teamsDeleteRequest($subdomain)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'DELETE',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -849,7 +849,7 @@ protected function teamsInviteMemberRequest($subdomain, $data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -870,7 +870,7 @@ protected function teamsInviteMemberRequest($subdomain, $data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1122,7 +1122,7 @@ protected function teamsListRequest($page = null, $limit = null)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1143,7 +1143,7 @@ protected function teamsListRequest($page = null, $limit = null)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1410,7 +1410,7 @@ protected function teamsPartialUpdateRequest($subdomain, $data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1431,7 +1431,7 @@ protected function teamsPartialUpdateRequest($subdomain, $data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'PATCH',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1684,7 +1684,7 @@ protected function teamsReadRequest($subdomain)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1705,7 +1705,7 @@ protected function teamsReadRequest($subdomain)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/TemplatesApi.php b/src/Api/TemplatesApi.php
index 9a74ffc..951e966 100644
--- a/src/Api/TemplatesApi.php
+++ b/src/Api/TemplatesApi.php
@@ -68,9 +68,9 @@ class TemplatesApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -328,7 +328,7 @@ protected function templatesListRequest($page = null, $limit = null)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -349,7 +349,7 @@ protected function templatesListRequest($page = null, $limit = null)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -602,7 +602,7 @@ protected function templatesReadRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -623,7 +623,7 @@ protected function templatesReadRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Api/WebhooksApi.php b/src/Api/WebhooksApi.php
index 7066c80..2cc8f12 100644
--- a/src/Api/WebhooksApi.php
+++ b/src/Api/WebhooksApi.php
@@ -68,9 +68,9 @@ class WebhooksApi
      * @param HeaderSelector  $selector
      */
     public function __construct(
-        ClientInterface $client = null,
-        Configuration $config = null,
-        HeaderSelector $selector = null
+        ?ClientInterface $client = null,
+        ?Configuration $config = null,
+        ?HeaderSelector $selector = null
     ) {
         $this->client = $client ?: new Client();
         $this->config = $config ?: new Configuration();
@@ -324,7 +324,7 @@ protected function webhooksCreateRequest($data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -345,7 +345,7 @@ protected function webhooksCreateRequest($data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'POST',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -561,7 +561,7 @@ protected function webhooksDeleteRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -582,7 +582,7 @@ protected function webhooksDeleteRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'DELETE',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -834,7 +834,7 @@ protected function webhooksListRequest($page = null, $limit = null)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -855,7 +855,7 @@ protected function webhooksListRequest($page = null, $limit = null)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1122,7 +1122,7 @@ protected function webhooksPartialUpdateRequest($uuid, $data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1143,7 +1143,7 @@ protected function webhooksPartialUpdateRequest($uuid, $data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'PATCH',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1396,7 +1396,7 @@ protected function webhooksReadRequest($uuid)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1417,7 +1417,7 @@ protected function webhooksReadRequest($uuid)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'GET',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
@@ -1684,7 +1684,7 @@ protected function webhooksUpdateRequest($uuid, $data)
 
             } else {
                 // for HTTP post (form)
-                $httpBody = \GuzzleHttp\Psr7\build_query($formParams);
+                $httpBody = \GuzzleHttp\Psr7\Query::build($formParams);
             }
         }
 
@@ -1705,7 +1705,7 @@ protected function webhooksUpdateRequest($uuid, $data)
             $headers
         );
 
-        $query = \GuzzleHttp\Psr7\build_query($queryParams);
+        $query = \GuzzleHttp\Psr7\Query::build($queryParams);
         return new Request(
             'PUT',
             $this->config->getHost() . $resourcePath . ($query ? "?{$query}" : ''),
diff --git a/src/Model/Document.php b/src/Model/Document.php
index 49b7e34..b6e3042 100644
--- a/src/Model/Document.php
+++ b/src/Model/Document.php
@@ -353,7 +353,7 @@ public function getStatusAllowableValues()
      * @param mixed[] $data Associated array of property values
      *                      initializing the model
      */
-    public function __construct(array $data = null)
+    public function __construct(?array $data = null)
     {
         $this->container['url'] = isset($data['url']) ? $data['url'] : null;
         $this->container['team'] = isset($data['team']) ? $data['team'] : null;
diff --git a/src/Model/DocumentSigningLog.php b/src/Model/DocumentSigningLog.php
index 728bdb1..bc6bb66 100644
--- a/src/Model/DocumentSigningLog.php
+++ b/src/Model/DocumentSigningLog.php
@@ -178,7 +178,7 @@ public function getModelName()
      * @param mixed[] $data Associated array of property values
      *                      initializing the model
      */
-    public function __construct(array $data = null)
+    public function __construct(?array $data = null)
     {
         $this->container['pdf'] = isset($data['pdf']) ? $data['pdf'] : null;
         $this->container['security_hash'] = isset($data['security_hash']) ? $data['security_hash'] : null;
diff --git a/src/Model/DocumentSignrequest.php b/src/Model/DocumentSignrequest.php
index 54d0b0c..0f2b681 100644
--- a/src/Model/DocumentSignrequest.php
+++ b/src/Model/DocumentSignrequest.php
@@ -290,7 +290,7 @@ public function getWhoAllowableValues()
      * @param mixed[] $data Associated array of property values
      *                      initializing the model
      */
-    public function __construct(array $data = null)
+    public function __construct(?array $data = null)
     {
         $this->container['from_email'] = isset($data['from_email']) ? $data['from_email'] : null;
         $this->container['from_email_name'] = isset($data['from_email_name']) ? $data['from_email_name'] : null;
diff --git a/src/Model/DocumentTeam.php b/src/Model/DocumentTeam.php
index 16c511e..2cdd6b1 100644
--- a/src/Model/DocumentTeam.php
+++ b/src/Model/DocumentTeam.php
@@ -183,7 +183,7 @@ public function getModelName()
      * @param mixed[] $data Associated array of property values
      *                      initializing the model
      */
-    public function __construct(array $data = null)
+    public function __construct(?array $data = null)
     {
         $this->container['name'] = isset($data['name']) ? $data['name'] : null;
         $this->container['subdomain'] = isset($data['subdomain']) ? $data['subdomain'] : null;
diff --git a/src/Model/Signer.php b/src/Model/Signer.php
index 57bd1b9..388d524 100644
--- a/src/Model/Signer.php
+++ b/src/Model/Signer.php
@@ -391,7 +391,7 @@ public function getLanguageAllowableValues()
      * @param mixed[] $data Associated array of property values
      *                      initializing the model
      */
-    public function __construct(array $data = null)
+    public function __construct(?array $data = null)
     {
         $this->container['email'] = isset($data['email']) ? $data['email'] : null;
         $this->container['display_name'] = isset($data['display_name']) ? $data['display_name'] : null;
@@ -1181,7 +1181,8 @@ public function setForwardedReason($forwarded_reason)
     {
 
         if (!is_null($forwarded_reason) && (mb_strlen($forwarded_reason) < 1)) {
-            throw new \InvalidArgumentException('invalid length for $forwarded_reason when calling Signer., must be bigger than or equal to 1.');
+            //throw new \InvalidArgumentException('invalid length for $forwarded_reason when calling Signer., must be bigger than or equal to 1.');
+			$forwarded_reason = ' N/A';
         }
 
         $this->container['forwarded_reason'] = $forwarded_reason;
diff --git a/src/Model/SignerInputs.php b/src/Model/SignerInputs.php
index 4d87a21..56d6a62 100644
--- a/src/Model/SignerInputs.php
+++ b/src/Model/SignerInputs.php
@@ -226,7 +226,7 @@ public function getTypeAllowableValues()
      * @param mixed[] $data Associated array of property values
      *                      initializing the model
      */
-    public function __construct(array $data = null)
+    public function __construct(?array $data = null)
     {
         $this->container['type'] = isset($data['type']) ? $data['type'] : null;
         $this->container['page_index'] = isset($data['page_index']) ? $data['page_index'] : null;