diff --git a/lib/Client.php b/lib/Client.php
index 1cf9b0c..de1437b 100644
--- a/lib/Client.php
+++ b/lib/Client.php
@@ -54,20 +54,21 @@ class Client
     /**
       * Initialize the client
       *
-      * @param string  $host                    the base url (e.g. https://api.sendgrid.com)
-      * @param array   $headers                 global request headers
-      * @param string  $version                 api version (configurable)
-      * @param array   $path                    holds the segments of the url path
+      * @param string  $host          the base url (e.g. https://api.sendgrid.com)
+      * @param array   $headers       global request headers
+      * @param string  $version       api version (configurable) - this is specific to the SendGrid API
+      * @param array   $path          holds the segments of the url path
+      * @param array   $curlOptions   extra options to set during curl initialization
+      * @param bool    $retryOnLimit  set default retry on limit flag
       */
-    public function __construct($host, $headers = [], $version = '/v3', $path = [])
+    public function __construct($host, $headers = null, $version = null, $path = null, $curlOptions = null, $retryOnLimit = false)
     {
         $this->host = $host;
-        $this->headers = $headers;
+        $this->headers = $headers ?: [];
         $this->version = $version;
-        $this->path = $path;
-
-        $this->curlOptions = [];
-        $this->retryOnLimit = false;
+        $this->path = $path ?: [];
+        $this->curlOptions = $curlOptions ?: [];
+        $this->retryOnLimit = $retryOnLimit;
         $this->isConcurrentRequest = false;
         $this->savedRequests = [];
     }
diff --git a/test/unit/ClientTest.php b/test/unit/ClientTest.php
index 43cebfe..2d39f67 100644
--- a/test/unit/ClientTest.php
+++ b/test/unit/ClientTest.php
@@ -20,7 +20,7 @@ protected function setUp()
             'Content-Type: application/json',
             'Authorization: Bearer SG.XXXX'
         ];
-        $this->client = new MockClient($this->host, $this->headers);
+        $this->client = new MockClient($this->host, $this->headers, '/v3');
     }
 
     public function testConstructor()
@@ -91,7 +91,7 @@ public function testGetVersion()
         $this->assertSame('/v3', $client->getVersion());
 
         $client = new Client('https://localhost:4010');
-        $this->assertSame('/v3', $client->getVersion());
+        $this->assertSame(null, $client->getVersion());
     }
 
     public function testGetPath()