diff --git a/prepare.php b/prepare.php
index 63db7ab..38e40c6 100644
--- a/prepare.php
+++ b/prepare.php
@@ -304,7 +304,7 @@ function curl_selected_bits(\$k) { return in_array(\$k, array('version', 'ssl_ve
 	) );
 
 	// Update the command to use the downloaded Composer phar file.
-	$composer_cmd .= $WPT_PHP_EXECUTABLE . ' composer.phar ';
+	$composer_cmd .= $runner_vars['WPT_PHP_EXECUTABLE'] . ' composer.phar ';
 }
 
 // Set the PHP version for Composer to ensure compatibility and update dependencies.