diff --git a/Civi/ContactCats/Processor.php b/Civi/ContactCats/Processor.php
index c1912dc..416905c 100644
--- a/Civi/ContactCats/Processor.php
+++ b/Civi/ContactCats/Processor.php
@@ -149,7 +149,7 @@ class Processor {
       CRM_Core_DAO::executeQuery("INSERT INTO civicrm_activity_contact (contact_id, activity_id, record_type_id)
         SELECT id contact_id, $activityID activity_id, 3 record_type_id
         FROM civicrm_contact_category cc
-        WHERE cc.category_definition_id = $oldCategoryId
+        WHERE COALESCE(cc.category_definition_id, 0) = $oldCategoryId
           AND cc.next_category = $newCategoryId
           AND cc.id <> $batch[0]
         ")->free();