diff --git a/CHANGELOG.md b/CHANGELOG.md
index a68921fd..7586c6c3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+### 3.8.9 ###
+- Fixed assignUserGroup permission serialization bug
+
 ### 3.8.8 ###
 - Added ability to exclude datatypes on import (thanks @Zae)
 
diff --git a/src/Services/Sources.php b/src/Services/Sources.php
index 1db2a8a8..3e387d99 100644
--- a/src/Services/Sources.php
+++ b/src/Services/Sources.php
@@ -110,6 +110,10 @@ public function getSource($fieldType, $source, $indexFrom, $indexTo)
               break;
           case 'editLocale':
               return $source;
+          case 'assignUserGroup':
+              $service = Craft::app()->userGroups;
+              $method = 'getGroupBy';
+              break;
        }
 
        if (isset($service) && isset($method) && isset($sourceFrom)) {