diff --git a/composer.json b/composer.json
index ae6f450b6..3f5e34175 100644
--- a/composer.json
+++ b/composer.json
@@ -10,7 +10,7 @@
     }
   ],
   "require": {
-    "php": "^5.6|^7.0",
+    "php": ">=5.6",
     "psr/log": "~1.0",
     "guzzlehttp/ringphp" : "~1.0"
   },
diff --git a/src/Elasticsearch/Client.php b/src/Elasticsearch/Client.php
index e22c3a125..badec43e9 100644
--- a/src/Elasticsearch/Client.php
+++ b/src/Elasticsearch/Client.php
@@ -32,7 +32,7 @@
  */
 class Client
 {
-    const VERSION = '5.5.0';
+    const VERSION = '5.5.1';
 
     /**
      * @var Transport
diff --git a/src/Elasticsearch/Connections/Connection.php b/src/Elasticsearch/Connections/Connection.php
index adb9d7ab0..656822858 100644
--- a/src/Elasticsearch/Connections/Connection.php
+++ b/src/Elasticsearch/Connections/Connection.php
@@ -326,7 +326,7 @@ private function wrapHandler(callable $handler, LoggerInterface $logger, LoggerI
     private function getURI($uri, $params)
     {
         if (isset($params) === true && !empty($params)) {
-            array_walk($params, function (&$value, &$key) {
+            array_walk($params, function (&$value) {
                 if ($value === true) {
                     $value = 'true';
                 } else if ($value === false) {
diff --git a/src/Elasticsearch/Connections/ConnectionInterface.php b/src/Elasticsearch/Connections/ConnectionInterface.php
index 44495dbdc..d6b96d3e8 100644
--- a/src/Elasticsearch/Connections/ConnectionInterface.php
+++ b/src/Elasticsearch/Connections/ConnectionInterface.php
@@ -95,5 +95,5 @@ public function getLastRequestInfo();
      * @param \Elasticsearch\Transport $transport
      * @return mixed
      */
-    public function performRequest($method, $uri, $params = null, $body = null, $options = [], Transport $transport);
+    public function performRequest($method, $uri, $params = null, $body = null, $options = [], Transport $transport = null);
 }
diff --git a/src/Elasticsearch/Transport.php b/src/Elasticsearch/Transport.php
index 2354a80f4..5ca3fad6c 100644
--- a/src/Elasticsearch/Transport.php
+++ b/src/Elasticsearch/Transport.php
@@ -48,7 +48,7 @@ class Transport
      * @param ConnectionPool\AbstractConnectionPool $connectionPool
      * @param \Psr\Log\LoggerInterface $log    Monolog logger object
      */
-    public function __construct($retries, $sniffOnStart = false, AbstractConnectionPool $connectionPool, LoggerInterface $log)
+    public function __construct($retries, $sniffOnStart = false, AbstractConnectionPool $connectionPool = null, LoggerInterface $log = null)
     {
         $this->log            = $log;
         $this->connectionPool = $connectionPool;