diff --git a/README.md b/README.md
index 23fe506..cbb1798 100644
--- a/README.md
+++ b/README.md
@@ -74,7 +74,7 @@ use RealtimeRegister\IsProxy;
 $isProxy = new IsProxy('my-secret-api-key');
 
 foreach ($isProxy->checkMany('example', ['nl', 'com', 'net', 'org']) as $result) {
-    echo $result->getDomain() . $result->isAvailable() ? ' ✅' : ' ❌';
+    echo $result->getDomain() . ($result->isAvailable() ? ' ✅' : ' ❌') . PHP_EOL;
 }
 // example.nl ✅
 // example.com ❌
diff --git a/src/IsProxy.php b/src/IsProxy.php
index e4f01e3..5863ea7 100644
--- a/src/IsProxy.php
+++ b/src/IsProxy.php
@@ -10,9 +10,9 @@ final class IsProxy
 {
     private IsProxyConnection $connection;
 
-    public function __construct(string $apiKey, string $host = 'is.yoursrs.com', int $port = 2001)
+    public function __construct(string $apiKey, string $host = 'is.yoursrs.com', int $port = 2001, bool $tls = true)
     {
-        $this->setConnection(new IsProxyConnection($apiKey, $host, $port));
+        $this->setConnection(new IsProxyConnection($apiKey, $host, $port, $tls));
     }
 
     public function setConnection(IsProxyConnection $connection): void
diff --git a/src/Support/IsProxyConnection.php b/src/Support/IsProxyConnection.php
index 68c5139..8e0a4fa 100644
--- a/src/Support/IsProxyConnection.php
+++ b/src/Support/IsProxyConnection.php
@@ -14,11 +14,14 @@ class IsProxyConnection
     /** @var resource */
     protected $socket;
 
-    public function __construct(string $apiKey, string $host = 'is.yoursrs.com', int $port = 2001)
+    protected bool $tls;
+
+    public function __construct(string $apiKey, string $host = 'is.yoursrs.com', int $port = 2001, bool $tls = true)
     {
         $this->apiKey = $apiKey;
         $this->host = $host;
         $this->port = $port;
+        $this->tls = $tls;
     }
 
     public function __destruct()
@@ -34,11 +37,23 @@ public function connect(): bool
         }
 
         $this->socket = $socket;
+
+        // Try to set up tls, if enabled;
+        if ($this->tls) {
+            if ($this->upgradeToTls() === false) {
+                return false;
+            }
+        }
+
         return $this->login();
     }
 
     public function disconnect(): void
     {
+        if (! $this->isConnected()) {
+            return;
+        }
+
         $this->write('CLOSE');
 
         @fclose($this->socket);
@@ -84,4 +99,28 @@ protected function login(): bool
 
         return (bool) preg_match('#^100\sLogin\sok#', $response);
     }
+
+    protected function upgradeToTls(): bool
+    {
+        if (! $this->write('STARTTLS')) {
+            return false;
+        }
+
+        $response = $this->read();
+        if (! preg_match('#^100\sOK#', $response)) {
+            return true;
+        }
+
+        $methods = STREAM_CRYPTO_METHOD_TLS_CLIENT;
+
+        if (defined('STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT')) {
+            $methods |= STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT;
+        }
+
+        if (defined('STREAM_CRYPTO_METHOD_TLSv1_3_CLIENT')) {
+            $methods |= STREAM_CRYPTO_METHOD_TLSv1_3_CLIENT;
+        }
+
+        return stream_socket_enable_crypto($this->socket, true, $methods) === true;
+    }
 }
diff --git a/tests/Clients/Domains/DomainsApiTransferTest.php b/tests/Clients/Domains/DomainsApiTransferTest.php
index 8e99d5b..f30b592 100644
--- a/tests/Clients/Domains/DomainsApiTransferTest.php
+++ b/tests/Clients/Domains/DomainsApiTransferTest.php
@@ -31,7 +31,6 @@ public function test_transfer_quote(): void
             authcode: '123123123',
             autoRenew: true,
             ns: [],
-            transferContacts: ['REGISTRANT'],
             designatedAgent: 'OLD',
             zone: Zone::fromArray(include __DIR__ . '/../../Domain/data/dns/zones/zone_valid.php'),
             contacts: DomainContactCollection::fromArray([include __DIR__ . '/../../Domain/data/domains/domain_contact_valid.php']),
@@ -64,7 +63,7 @@ public function test_transfer(): void
             '123123123',
             true,
             [],
-            ['ADMIN'],
+            null,
             'OLD',
             Zone::fromArray(include __DIR__ . '/../../Domain/data/dns/zones/zone_valid.php'),
             DomainContactCollection::fromArray([include __DIR__ . '/../../Domain/data/domains/domain_contact_valid.php']),
diff --git a/tests/Helpers/MockedIsProxyConnection.php b/tests/Helpers/MockedIsProxyConnection.php
index b0b9692..2470833 100644
--- a/tests/Helpers/MockedIsProxyConnection.php
+++ b/tests/Helpers/MockedIsProxyConnection.php
@@ -19,9 +19,9 @@ class MockedIsProxyConnection extends IsProxyConnection
     /** @var bool */
     private $connected = false;
 
-    public function __construct(string $apiKey, TestCase $testCase)
+    public function __construct(string $apiKey, TestCase $testCase, bool $tls = true)
     {
-        parent::__construct($apiKey);
+        parent::__construct($apiKey, tls: $tls);
 
         $this->testCase = $testCase;
     }
@@ -55,6 +55,13 @@ public function expectWrite(string $message): MockedIsProxyConnection
     public function connect(): bool
     {
         $this->connected = true;
+
+        if ($this->tls) {
+            if ($this->upgradeToTls() === false) {
+                return false;
+            }
+        }
+
         return $this->login();
     }
 
@@ -81,4 +88,19 @@ public function isConnected(): bool
     {
         return $this->connected;
     }
+
+    protected function upgradeToTls(): bool
+    {
+        if (! $this->write('STARTTLS')) {
+            return false;
+        }
+
+        $response = $this->read();
+
+        if ($response !== '100 OK') {
+            return false;
+        }
+
+        return true;
+    }
 }
diff --git a/tests/IsProxyConnectionTest.php b/tests/IsProxyConnectionTest.php
index aeac1e9..abb3cbb 100644
--- a/tests/IsProxyConnectionTest.php
+++ b/tests/IsProxyConnectionTest.php
@@ -13,6 +13,8 @@ class IsProxyConnectionTest extends TestCase
     public function test_check(): void
     {
         $connection = (new MockedIsProxyConnection('secret', $this))
+            ->expectWrite('STARTTLS')
+            ->expectRead('100 OK')
             ->expectWrite('LOGIN secret')
             ->expectRead('100 Login ok')
             ->expectWrite('IS example.com')
@@ -33,6 +35,8 @@ public function test_check(): void
     public function test_connection_error(): void
     {
         $connection = (new MockedIsProxyConnection('secret', $this))
+            ->expectWrite('STARTTLS')
+            ->expectRead('100 OK')
             ->expectWrite('LOGIN secret')
             ->expectRead('400 Login failed');
 
@@ -46,6 +50,8 @@ public function test_connection_error(): void
     public function test_check_wrong_answer(): void
     {
         $connection = (new MockedIsProxyConnection('secret', $this))
+            ->expectWrite('STARTTLS')
+            ->expectRead('100 OK')
             ->expectWrite('LOGIN secret')
             ->expectRead('100 Login ok')
             ->expectWrite('IS example.com')
@@ -63,6 +69,8 @@ public function test_check_wrong_answer(): void
     public function test_check_many(): void
     {
         $connection = (new MockedIsProxyConnection('secret', $this))
+            ->expectWrite('STARTTLS')
+            ->expectRead('100 OK')
             ->expectWrite('LOGIN secret')
             ->expectRead('100 Login ok')
             ->expectWrite('IS example.com')
@@ -110,6 +118,8 @@ public function test_check_many(): void
     public function test_check_many_connection_fail(): void
     {
         $connection = (new MockedIsProxyConnection('secret', $this))
+            ->expectWrite('STARTTLS')
+            ->expectRead('100 OK')
             ->expectWrite('LOGIN secret')
             ->expectRead('400 Login failed');
 
@@ -123,6 +133,8 @@ public function test_check_many_connection_fail(): void
     public function test_check_premium(): void
     {
         $connection = (new MockedIsProxyConnection('secret', $this))
+            ->expectWrite('STARTTLS')
+            ->expectRead('100 OK')
             ->expectWrite('LOGIN secret')
             ->expectRead('100 Login ok')
             ->expectWrite('ENABLE premium')
@@ -182,4 +194,24 @@ public function test_check_premium(): void
         $this->assertEmpty($availableDomain->getExtras());
         $this->assertTrue($invalidDomain->isInvalid());
     }
+
+    public function test_check_without_ssl_support(): void
+    {
+        $connection = (new MockedIsProxyConnection('secret', $this, false))
+            ->expectWrite('LOGIN secret')
+            ->expectRead('100 Login ok')
+            ->expectWrite('IS example.com')
+            ->expectRead('example.com available')
+            ->expectWrite('CLOSE');
+
+        $isProxy = new IsProxy(apiKey:'secret', tls: false);
+        $isProxy->setConnection($connection);
+
+        $result = $isProxy->check('example', 'com');
+
+        $this->assertInstanceOf(IsProxyDomain::class, $result);
+        $this->assertSame(IsProxyDomain::STATUS_AVAILABLE, $result->getStatus());
+        $this->assertSame('example.com', $result->getDomain());
+        $this->assertTrue($result->isAvailable());
+    }
 }