diff --git a/pronamic-money.php b/pronamic-money.php
index c01eeb5..99f1ae3 100644
--- a/pronamic-money.php
+++ b/pronamic-money.php
@@ -24,6 +24,10 @@
  * @package   Pronamic\WordPress\Pay
  */
 
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
 /**
  * Pronamic Money load plugin text domain.
  */