diff --git a/mongoengine/base/document.py b/mongoengine/base/document.py
index 4f5a87e5..60b4d975 100644
--- a/mongoengine/base/document.py
+++ b/mongoengine/base/document.py
@@ -84,6 +84,17 @@ class BaseDocument(object):
         self._initialised = True
         signals.post_init.send(self.__class__, document=self)
 
+    def __delattr__(self, *args, **kwargs):
+        """Handle deletions of fields"""
+        field_name = args[0]
+        if field_name in self._fields:
+            default = self._fields[field_name].default
+            if callable(default):
+                default = default()
+            setattr(self, field_name, default)
+        else:
+            super(BaseDocument, self).__delattr__(*args, **kwargs)
+
     def __setattr__(self, name, value):
         # Handle dynamic data only if an initialised dynamic document
         if self._dynamic and not self._dynamic_lock:
diff --git a/mongoengine/document.py b/mongoengine/document.py
index edc819cb..66aa2632 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -250,16 +250,16 @@ class Document(BaseDocument):
                     return created
 
                 upsert = self._created
+                update_query = {}
+
                 if updates:
-                    last_error = collection.update(select_dict,
-                        {"$set": updates}, upsert=upsert, safe=safe,
-                        **write_options)
-                    created = is_new_object(last_error)
+                    update_query["$set"] = updates
                 if removals:
-                    last_error = collection.update(select_dict,
-                        {"$unset": removals}, upsert=upsert, safe=safe,
-                        **write_options)
-                    created = created or is_new_object(last_error)
+                    update_query["$unset"] = removals
+                if updates or removals:
+                    last_error = collection.update(select_dict, update_query,
+                                    upsert=upsert, safe=safe, **write_options)
+                    created = is_new_object(last_error)
 
             warn_cascade = not cascade and 'cascade' not in self._meta
             cascade = (self._meta.get('cascade', True)
diff --git a/tests/document/instance.py b/tests/document/instance.py
index 172f0ccf..9a4149ff 100644
--- a/tests/document/instance.py
+++ b/tests/document/instance.py
@@ -18,7 +18,7 @@ from mongoengine.errors import (NotRegistered, InvalidDocumentError,
 from mongoengine.queryset import NULLIFY, Q
 from mongoengine.connection import get_db
 from mongoengine.base import get_document
-from mongoengine.context_managers import switch_db
+from mongoengine.context_managers import switch_db, query_counter
 from mongoengine import signals
 
 TEST_IMAGE_PATH = os.path.join(os.path.dirname(__file__),
@@ -971,6 +971,28 @@ class InstanceTest(unittest.TestCase):
         self.assertEqual(person.age, 21)
         self.assertEqual(person.active, False)
 
+    def test_set_unset_one_operation(self):
+        """Ensure that $set and $unset actions are performed in the same
+        operation.
+        """
+        class FooBar(Document):
+            foo = StringField(default=None)
+            bar = StringField(default=None)
+
+        FooBar.drop_collection()
+
+        # write an entity with a single prop
+        foo = FooBar(foo='foo').save()
+
+        self.assertEqual(foo.foo, 'foo')
+        del foo.foo
+        foo.bar = 'bar'
+
+        with query_counter() as q:
+            self.assertEqual(0, q)
+            foo.save()
+            self.assertEqual(1, q)
+
     def test_save_only_changed_fields_recursive(self):
         """Ensure save only sets / unsets changed fields
         """
diff --git a/tests/queryset/queryset.py b/tests/queryset/queryset.py
index c6b7c0e0..3d5c659c 100644
--- a/tests/queryset/queryset.py
+++ b/tests/queryset/queryset.py
@@ -260,7 +260,8 @@ class QuerySetTest(unittest.TestCase):
                             name='Test User', write_options=write_options)
         author.save(write_options=write_options)
 
-        self.Person.objects.update(set__name='Ross', write_options=write_options)
+        self.Person.objects.update(set__name='Ross',
+                                    write_options=write_options)
 
         author = self.Person.objects.first()
         self.assertEqual(author.name, 'Ross')