diff --git a/Civi/ActionProvider/Utils/CustomField.php b/Civi/ActionProvider/Utils/CustomField.php
index 85baa8a4739408fb6e67fd0935956b3424e623fb..3d8c224a6cb9eab9de36aa588efb4a23c81e816f 100644
--- a/Civi/ActionProvider/Utils/CustomField.php
+++ b/Civi/ActionProvider/Utils/CustomField.php
@@ -71,6 +71,10 @@ class CustomField {
     if ($customField['html_type'] == 'Multi-Select') {
       $multiple = true;
     }
+    // File custom fields shouldn't be selectable - use the "upload file to a custom field" action instead.
+    if ($customField['html_type'] == 'File') {
+      return null;
+    }
     $default = null;
     $spec = null;