diff --git a/pronamic-datetime.php b/pronamic-datetime.php
index 988f89e..e4902ce 100644
--- a/pronamic-datetime.php
+++ b/pronamic-datetime.php
@@ -24,6 +24,10 @@
  * @package   Pronamic\WordPress\Pay
  */
 
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
 /**
  * Pronamic DateTime load plugin text domain.
  */