diff --git a/src/PersistentData/PersistentDataManager.php b/src/PersistentData/PersistentDataManager.php
index 0a75214..5932f06 100644
--- a/src/PersistentData/PersistentDataManager.php
+++ b/src/PersistentData/PersistentDataManager.php
@@ -227,12 +227,16 @@ class PersistentDataManager implements IPersistentDataManager
 
                 next($data);
             } else if (substr($key, 0, strlen($relation . '__')) === $relation . '__') {
-                $relationType = current($relations);
-                $relationModel = new $relationType();
-                $this->fillWithData($data, $relationModel, $withRelations, $relation);
+                if ($data[$relation . '__id'] !== null) {
+                    $relationType = current($relations);
+                    $relationModel = new $relationType();
+                    $this->fillWithData($data, $relationModel, $withRelations, $relation);
 
-                $method = 'set' . str_replace('_', '', ucwords($relation, '_'));
-                $model->$method($relationModel);
+                    $method = 'set' . str_replace('_', '', ucwords($relation, '_'));
+                    $model->$method($relationModel);
+                } else {
+                    next($data);
+                }
 
                 next($relations);
             } else {