diff --git a/gf-giftaid-field.php b/gf-giftaid-field.php
index e499a2a..d42f054 100644
--- a/gf-giftaid-field.php
+++ b/gf-giftaid-field.php
@@ -25,7 +25,7 @@
 }
 
 if (! defined('ITINERIS_GF_GIFT_AID_FIELD_URI')) {
-    define('ITINERIS_GF_GIFT_AID_FIELD_URI', WPMU_PLUGIN_URL . '/' . basename(__DIR__));
+    define('ITINERIS_GF_GIFT_AID_FIELD_URI', plugins_url(basename(__DIR__)));
 }
 
 add_action('gform_loaded', [GfGiftAidField::class, 'load'], 5);