diff --git a/src/Elasticsearch/Client.php b/src/Elasticsearch/Client.php
index bfd771234..5838b933c 100644
--- a/src/Elasticsearch/Client.php
+++ b/src/Elasticsearch/Client.php
@@ -1457,7 +1457,7 @@ public function extractArgument(&$params, $arg)
             $params = (array) $params;
         }
 
-        if (isset($params[$arg]) === true) {
+        if (array_key_exists($arg, $params) === true) {
             $val = $params[$arg];
             unset($params[$arg]);
 
diff --git a/src/Elasticsearch/Namespaces/AbstractNamespace.php b/src/Elasticsearch/Namespaces/AbstractNamespace.php
index 42a0c7815..13b2e02f6 100644
--- a/src/Elasticsearch/Namespaces/AbstractNamespace.php
+++ b/src/Elasticsearch/Namespaces/AbstractNamespace.php
@@ -46,7 +46,7 @@ public function extractArgument(&$params, $arg)
             $params = (array) $params;
         }
 
-        if (isset($params[$arg]) === true) {
+        if (array_key_exists($arg, $params) === true) {
             $val = $params[$arg];
             unset($params[$arg]);