diff --git a/src/Symfony/Component/Console/Input/InputDefinition.php b/src/Symfony/Component/Console/Input/InputDefinition.php
index a18da2b2f3..257d057ffc 100644
--- a/src/Symfony/Component/Console/Input/InputDefinition.php
+++ b/src/Symfony/Component/Console/Input/InputDefinition.php
@@ -153,12 +153,12 @@ class InputDefinition
      */
     public function getArgument($name)
     {
-        $arguments = is_int($name) ? array_values($this->arguments) : $this->arguments;
-
         if (!$this->hasArgument($name)) {
             throw new \InvalidArgumentException(sprintf('The "%s" argument does not exist.', $name));
         }
 
+        $arguments = is_int($name) ? array_values($this->arguments) : $this->arguments;
+
         return $arguments[$name];
     }