diff --git a/src/Elasticsearch/ClientBuilder.php b/src/Elasticsearch/ClientBuilder.php
index bc36abaf8..7a716b666 100644
--- a/src/Elasticsearch/ClientBuilder.php
+++ b/src/Elasticsearch/ClientBuilder.php
@@ -442,6 +442,23 @@ public function build()
             if (is_null($this->connectionParams)) {
                 $this->connectionParams = [];
             }
+
+            // Make sure we are setting Content-type and Accept (unless the user has explicitly
+            // overridden it
+            if (isset($this->connectionParams['client']['headers']) === false) {
+                $this->connectionParams['client']['headers'] = [
+                    'Content-type' => ['application/json'],
+                    'Accept' => ['application/json']
+                ];
+            } else {
+                if (isset($this->connectionParams['client']['headers']['Content-type']) === false) {
+                    $this->connectionParams['client']['headers']['Content-type'] = ['application/json'];
+                }
+                if (isset($this->connectionParams['client']['headers']['Accept']) === false) {
+                    $this->connectionParams['client']['headers']['Accept'] = ['application/json'];
+                }
+            }
+
             $this->connectionFactory = new ConnectionFactory($this->handler, $this->connectionParams, $this->serializer, $this->logger, $this->tracer);
         }
 
diff --git a/src/Elasticsearch/Connections/Connection.php b/src/Elasticsearch/Connections/Connection.php
index 2d9e28984..f8aa71a69 100644
--- a/src/Elasticsearch/Connections/Connection.php
+++ b/src/Elasticsearch/Connections/Connection.php
@@ -72,6 +72,9 @@ class Connection implements ConnectionInterface
      */
     protected $connectionParams;
 
+    /** @var  array */
+    protected $headers = [];
+
     /** @var bool  */
     protected $isAlive = false;
 
@@ -112,6 +115,11 @@ public function __construct($handler, $hostDetails, $connectionParams,
             $connectionParams['client']['curl'][CURLOPT_USERPWD] = $hostDetails['user'].':'.$hostDetails['pass'];
         }
 
+        if (isset($connectionParams['client']['headers']) === true) {
+            $this->headers = $connectionParams['client']['headers'];
+            unset($connectionParams['client']['headers']);
+        }
+
         $host = $hostDetails['host'].':'.$hostDetails['port'];
         $path = null;
         if (isset($hostDetails['path']) === true) {
@@ -147,13 +155,17 @@ public function performRequest($method, $uri, $params = null, $body = null, $opt
             'scheme'      => $this->transportSchema,
             'uri'         => $this->getURI($uri, $params),
             'body'        => $body,
-            'headers'     => [
+            'headers'     => array_merge([
                 'host'  => [$this->host]
-            ]
-
+            ], $this->headers)
         ];
+
         $request = array_merge_recursive($request, $this->connectionParams, $options);
 
+        // RingPHP does not like if client is empty
+        if (empty($request['client'])) {
+            unset($request['client']);
+        }
 
         $handler = $this->handler;
         $future = $handler($request, $this, $transport, $options);
diff --git a/tests/Elasticsearch/Tests/YamlRunnerTest.php b/tests/Elasticsearch/Tests/YamlRunnerTest.php
index c22d5e4bf..685ea0061 100644
--- a/tests/Elasticsearch/Tests/YamlRunnerTest.php
+++ b/tests/Elasticsearch/Tests/YamlRunnerTest.php
@@ -291,6 +291,11 @@ public function operationDo($operation, $lastOperationResult, &$context, $testNa
             self::markTestIncomplete(sprintf('Method "%s" not implement in "%s"', $method, get_class($caller)));
         }
 
+        // TODO remove this after cat testing situation resolved
+        if ($caller instanceof Elasticsearch\Namespaces\CatNamespace) {
+            $endpointParams->format = 'text';
+        }
+
         // Exist* methods have to be manually 'unwrapped' into true/false for async
         if (strpos($method, "exist") !== false && $async === true) {
             return $this->executeAsyncExistRequest($caller, $method, $endpointParams, $expectedError, $expectedWarnings, $testName);
@@ -384,32 +389,31 @@ public function checkForWarnings($expectedWarnings) {
         $last = $this->client->transport->getLastConnection()->getLastRequestInfo();
 
 
-            // We have some warnings to check
-            if ($expectedWarnings !== null) {
-                if (isset($last['response']['headers']['Warning']) === true) {
-                    foreach ($last['response']['headers']['Warning'] as $warning) {
-                        $position = array_search($warning, $expectedWarnings);
-                        if ($position !== false) {
-                            // found the warning
-                            unset($expectedWarnings[$position]);
-                        } else {
-                            // didn't find, throw error
-                            //throw new \Exception("Expected to find warning [$warning] but did not.");
-                        }
-                    }
-                    if (count($expectedWarnings) > 0) {
-                        throw new \Exception("Expected to find more warnings: ". print_r($expectedWarnings, true));
+        // We have some warnings to check
+        if ($expectedWarnings !== null) {
+            if (isset($last['response']['headers']['Warning']) === true) {
+                foreach ($last['response']['headers']['Warning'] as $warning) {
+                    $position = array_search($warning, $expectedWarnings);
+                    if ($position !== false) {
+                        // found the warning
+                        unset($expectedWarnings[$position]);
+                    } else {
+                        // didn't find, throw error
+                        //throw new \Exception("Expected to find warning [$warning] but did not.");
                     }
                 }
-            }
-            /* else {
-                // no expected warnings, make sure we have none returned
-                if (isset($last['response']['headers']['Warning']) === true) {
-                    throw new \Exception("Did not expect to find warnings, found some instead: "
-                        . print_r($last['response']['headers']['Warning'], true));
+                if (count($expectedWarnings) > 0) {
+                    throw new \Exception("Expected to find more warnings: ". print_r($expectedWarnings, true));
                 }
             }
-            */
+        }
+
+        // Check to make sure we're adding headers
+        static::assertArrayHasKey('Content-type', $last['request']['headers'], print_r($last['request']['headers'], true));
+        static::assertEquals('application/json', $last['request']['headers']['Content-type'][0], print_r($last['request']['headers'], true));
+        static::assertArrayHasKey('Accept', $last['request']['headers'], print_r($last['request']['headers'], true));
+        static::assertEquals('application/json', $last['request']['headers']['Accept'][0], print_r($last['request']['headers'], true));
+
     }
 
     /**