diff --git a/src/ChangesCollector.php b/src/ChangesCollector.php
index 2d8e423..e615b57 100644
--- a/src/ChangesCollector.php
+++ b/src/ChangesCollector.php
@@ -25,8 +25,6 @@ public function changes($object)
                 return Converter::convertJsonPatchToMongoUpdate($diff);
             }
 
-            unset($values['_id']);
-
             return ['$set' => $values];
         })->call($object);
     }
diff --git a/src/Hydrator.php b/src/Hydrator.php
index 71275bf..b57590c 100644
--- a/src/Hydrator.php
+++ b/src/Hydrator.php
@@ -3,6 +3,7 @@
 
 use function Makasim\Values\build_object;
 use function Makasim\Values\set_values;
+use MongoDB\BSON\ObjectID;
 
 class Hydrator
 {
@@ -41,7 +42,9 @@ public function hydrate(array $values, $model = null)
         $model = $model ?: $this->create($values);
 
         if (isset($values['_id'])) {
-            $values['_id'] = (string) $values['_id'];
+            set_object_id($model, new ObjectID((string) $values['_id']));
+
+            unset($values['_id']);
         }
 
         set_values($model, $values);
diff --git a/src/Storage.php b/src/Storage.php
index e429bf8..80a1789 100644
--- a/src/Storage.php
+++ b/src/Storage.php
@@ -67,7 +67,7 @@ public function insert($model, array $options = [])
             throw new \LogicException('Operation is not acknowledged');
         }
 
-        set_object_id($model, $result->getInsertedId());
+        set_object_id($model, new ObjectID((string) $result->getInsertedId()));
         $this->changesCollector->register($model);
 
         return $result;
@@ -111,7 +111,7 @@ public function insertMany(array $models, array $options = [])
     public function update($model, $filter = null, array $options = [])
     {
         if (null === $filter) {
-            $filter = ['_id' => new ObjectID(get_object_id($model))];
+            $filter = ['_id' => get_object_id($model)];
         }
 
         $update = $this->changesCollector->changes($model);
@@ -119,13 +119,10 @@ public function update($model, $filter = null, array $options = [])
             return;
         }
 
-        if (false == $update) {
-            return;
-        }
-
         $result = $this->collection->updateOne($filter, $update, $options);
-        if (false == $result->isAcknowledged()) {
-            throw new \LogicException('Operation is not acknowledged');
+
+        if ($result->getUpsertedCount()) {
+            set_object_id($model, new ObjectID((string) $result->getUpsertedId()));
         }
 
         $this->changesCollector->register($model);
@@ -141,14 +138,7 @@ public function update($model, $filter = null, array $options = [])
      */
     public function delete($model, array $options = [])
     {
-        $modelId = new ObjectID(get_object_id($model));
-
-        $result = $this->collection->deleteOne(['_id' => $modelId], $options);
-        if (false == $result->isAcknowledged()) {
-            throw new \LogicException('Operation is not acknowledged');
-        }
-
-        return $result;
+        return $this->collection->deleteOne(['_id' => get_object_id($model)], $options);
     }
 
     /**
diff --git a/src/functions.php b/src/functions.php
index a419a1b..9a8fd87 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -4,23 +4,29 @@
 
 /**
  * @param object $object
+ * @param bool $orNull
  *
- * @return string
+ * @return ObjectID|null
  */
-function get_object_id($object)
+function get_object_id($object, $orNull = false)
 {
-    return (function () {
-        return (string) isset($this->values['_id']) ? $this->values['_id'] : null;
+    return (function () use ($orNull) {
+        $id = isset($this->_id) ? $this->_id : null;
+
+
+        if (false == $id && false == $orNull) {
+            throw new \LogicException('The object id is not set.');
+        }
+
+        return $id;
     })->call($object);
 }
 
 /**
- * @param object          $object
- * @param ObjectID|string $objectId
+ * @param object   $object
+ * @param ObjectID $id
  */
-function set_object_id($object, $objectId)
+function set_object_id($object, ObjectID $id)
 {
-    return (function () use ($objectId) {
-        $this->values['_id'] = (string) $objectId;
-    })->call($object);
-}
\ No newline at end of file
+    (function () use ($id) { $this->_id = $id; })->call($object);
+}