diff --git a/src/Definition/Argument.php b/src/Definition/Argument.php
index 6b64b8667..7ee786638 100644
--- a/src/Definition/Argument.php
+++ b/src/Definition/Argument.php
@@ -53,7 +53,7 @@ public function getRawArguments(): array
      */
     public function offsetExists($offset): bool
     {
-        return isset($this->rawArguments[$offset]);
+        return \array_key_exists($offset, $this->rawArguments);
     }
 
     /**