diff --git a/AUTHORS b/AUTHORS
index af87d503..9d105a60 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -119,7 +119,7 @@ that much better:
  * Anton Kolechkin
  * Sergey Nikitin
  * psychogenic
- * Stefan Wójcik
+ * Stefan Wójcik (https://github.com/wojcikstefan)
  * dimonb
  * Garry Polley
  * James Slagle
@@ -138,7 +138,6 @@ that much better:
  * hellysmile
  * Jaepil Jeong
  * Daniil Sharou
- * Stefan Wójcik
  * Pete Campton
  * Martyn Smith
  * Marcelo Anton
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 2a6f7802..f4b5ec6c 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -14,6 +14,7 @@ Changes in 0.9.X - DEV
 - Fixed unpickled documents replacing the global field's list. #888
 - Fixed storage of microseconds in ComplexDateTimeField and unused separator option. #910
 - Django support was removed and will be available as a separate extension. #958
+- Don't send a "cls" option to ensureIndex (related to https://jira.mongodb.org/browse/SERVER-769)
 
 Changes in 0.9.0
 ================
diff --git a/mongoengine/document.py b/mongoengine/document.py
index f8275021..01083d24 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -677,6 +677,12 @@ class Document(BaseDocument):
                 cls_indexed = cls_indexed or includes_cls(fields)
                 opts = index_opts.copy()
                 opts.update(spec)
+
+                # we shouldn't pass 'cls' to the collection.ensureIndex options
+                # because of https://jira.mongodb.org/browse/SERVER-769
+                if 'cls' in opts:
+                    del opts['cls']
+
                 collection.ensure_index(fields, background=background,
                                         drop_dups=drop_dups, **opts)
 
@@ -684,6 +690,12 @@ class Document(BaseDocument):
         # only if another index doesn't begin with _cls
         if (index_cls and not cls_indexed and
                 cls._meta.get('allow_inheritance', ALLOW_INHERITANCE) is True):
+
+            # we shouldn't pass 'cls' to the collection.ensureIndex options
+            # because of https://jira.mongodb.org/browse/SERVER-769
+            if 'cls' in index_opts:
+                del index_opts['cls']
+
             collection.ensure_index('_cls', background=background,
                                     **index_opts)
 
diff --git a/tests/document/indexes.py b/tests/document/indexes.py
index ab156f68..6256cde3 100644
--- a/tests/document/indexes.py
+++ b/tests/document/indexes.py
@@ -826,5 +826,63 @@ class IndexesTest(unittest.TestCase):
         post2 = BlogPost(title='test2', slug='test')
         self.assertRaises(NotUniqueError, post2.save)
 
+    def test_index_dont_send_cls_option(self):
+        """
+        Ensure that 'cls' option is not sent through ensureIndex. We shouldn't
+        send internal MongoEngine arguments that are not a part of the index
+        spec.
+
+        This is directly related to the fact that MongoDB doesn't validate the
+        options that are passed to ensureIndex. For more details, see:
+        https://jira.mongodb.org/browse/SERVER-769
+        """
+        class TestDoc(Document):
+            txt = StringField()
+
+            meta = {
+                'allow_inheritance': True,
+                'indexes': [
+                    { 'fields': ('txt',), 'cls': False }
+                ]
+            }
+
+        class TestChildDoc(TestDoc):
+            txt2 = StringField()
+
+            meta = {
+                'indexes': [
+                    { 'fields': ('txt2',), 'cls': False }
+                ]
+            }
+
+        TestDoc.drop_collection()
+        TestDoc.ensure_indexes()
+        TestChildDoc.ensure_indexes()
+
+        index_info = TestDoc._get_collection().index_information()
+        for key in index_info:
+            del index_info[key]['v']  # drop the index version - we don't care about that here
+
+        self.assertEqual(index_info, {
+            'txt_1': {
+                'key': [('txt', 1)],
+                'dropDups': False,
+                'background': False
+            },
+            '_id_': {
+                'key': [('_id', 1)],
+            },
+            'txt2_1': {
+                'key': [('txt2', 1)],
+                'dropDups': False,
+                'background': False
+            },
+            '_cls_1': {
+                'key': [('_cls', 1)],
+                'background': False,
+            }
+        })
+
+
 if __name__ == '__main__':
     unittest.main()