diff --git a/mongoengine/document.py b/mongoengine/document.py
index 2e3eee9d..ff39b13a 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -312,8 +312,9 @@ class Document(BaseDocument):
                     # In PyMongo 3.0, the save() call calls internally the _update() call
                     # but they forget to return the _id value passed back, therefore getting it back here
                     if not object_id and pymongo.version_tuple == (3, 0):
-                        object_id = self._qs.filter(**self._object_key).first() and \
-                                    self._qs.filter(**self._object_key).first().pk
+                        pk_as_mongo_obj = self._fields.get(self._meta['id_field']).to_mongo(self.pk)
+                        object_id = self._qs.filter(pk=pk_as_mongo_obj).first() and \
+                                    self._qs.filter(pk=pk_as_mongo_obj).first().pk
             else:
                 object_id = doc['_id']
                 updates, removals = self._delta()
diff --git a/tests/fields/fields.py b/tests/fields/fields.py
index 0dc239c4..071f1dd0 100644
--- a/tests/fields/fields.py
+++ b/tests/fields/fields.py
@@ -1,5 +1,7 @@
 # -*- coding: utf-8 -*-
 import sys
+from nose.plugins.skip import SkipTest
+
 sys.path[0:0] = [""]
 
 import datetime
@@ -2491,8 +2493,25 @@ class FieldTest(unittest.TestCase):
         binary_id = uuid.uuid4().bytes
         att = Attachment(id=binary_id).save()
         self.assertEqual(1, Attachment.objects.count())
+        self.assertEqual(1, Attachment.objects.filter(id=att.id).count())
         # TODO use assertIsNotNone once Python 2.6 support is dropped
-        self.assertFalse(Attachment.objects.filter(id=binary_id).first() is not None)
+        self.assertTrue(Attachment.objects.filter(id=att.id).first() is not None)
+        att.delete()
+        self.assertEqual(0, Attachment.objects.count())
+
+    def test_binary_field_primary_filter_by_binary_pk_as_str(self):
+
+        raise SkipTest("Querying by id as string is not currently supported")
+
+        class Attachment(Document):
+            id = BinaryField(primary_key=True)
+
+        Attachment.drop_collection()
+        binary_id = uuid.uuid4().bytes
+        att = Attachment(id=binary_id).save()
+        self.assertEqual(1, Attachment.objects.filter(id=binary_id).count())
+        # TODO use assertIsNotNone once Python 2.6 support is dropped
+        self.assertTrue(Attachment.objects.filter(id=binary_id).first() is not None)
         att.delete()
         self.assertEqual(0, Attachment.objects.count())