diff --git a/mongoengine/document.py b/mongoengine/document.py
index b671ac6b..84c1d699 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -808,7 +808,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
         db.drop_collection(col_name)
 
     @classmethod
-    def _create_index(cls, keys, background=False, **kwargs):
+    def create_index(cls, keys, background=False, **kwargs):
         """Creates the given indexes if required.
 
         :param keys: a single index key or a list of index keys (to
@@ -851,7 +851,7 @@ class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
             warnings.warn(msg, DeprecationWarning)
         elif not IS_PYMONGO_3:
             kwargs.update({'drop_dups': drop_dups})
-        return cls._create_index(key_or_list, background=background, **kwargs)
+        return cls.create_index(key_or_list, background=background, **kwargs)
 
     @classmethod
     def ensure_indexes(cls):
diff --git a/tests/document/indexes.py b/tests/document/indexes.py
index 36fbae46..abd349f3 100644
--- a/tests/document/indexes.py
+++ b/tests/document/indexes.py
@@ -611,7 +611,11 @@ class IndexesTest(unittest.TestCase):
 
         with self.assertRaises(OperationFailure) as ctx_err:
             Blog(id='garbage').save()
-        self.assertIn("The field 'unique' is not valid for an _id index specification", str(ctx_err.exception))
+        try:
+            self.assertIn("The field 'unique' is not valid for an _id index specification", str(ctx_err.exception))
+        except AssertionError:
+            # error is slightly different on python 3.6
+            self.assertIn("The field 'background' is not valid for an _id index specification", str(ctx_err.exception))
 
     @requires_mongodb_lte_32
     def test_primary_key_unique_working_under_mongo_32(self):