diff --git a/bigchaindb/backend/localmongodb/connection.py b/bigchaindb/backend/localmongodb/connection.py
index c868161f..f638dcac 100644
--- a/bigchaindb/backend/localmongodb/connection.py
+++ b/bigchaindb/backend/localmongodb/connection.py
@@ -22,7 +22,7 @@ class LocalMongoDBConnection(Connection):
 
     def __init__(self, replicaset=None, ssl=None, login=None, password=None,
                  ca_cert=None, certfile=None, keyfile=None,
-                 keyfile_passphrase=None, crlfile=None, auth_mechanism=None, auth_source=None, **kwargs):
+                 keyfile_passphrase=None, crlfile=None, **kwargs):
         """Create a new Connection instance.
 
         Args:
@@ -42,8 +42,6 @@ class LocalMongoDBConnection(Connection):
         self.keyfile = keyfile or get_bigchaindb_config_value('keyfile')
         self.keyfile_passphrase = keyfile_passphrase or get_bigchaindb_config_value('keyfile_passphrase')
         self.crlfile = crlfile or get_bigchaindb_config_value('crlfile')
-        self.auth_mechanism = auth_mechanism or get_bigchaindb_config_value('auth_mechanism')
-        self.auth_source = auth_source or get_bigchaindb_config_value('auth_source')
 
     @property
     def db(self):
diff --git a/setup.py b/setup.py
index a2ec29ab..b4c81471 100644
--- a/setup.py
+++ b/setup.py
@@ -73,7 +73,7 @@ tests_require = [
 
 install_requires = [
     # TODO Consider not installing the db drivers, or putting them in extras.
-    'pymongo~=3.6',
+    'pymongo~=3.9',
     'cryptoconditions==0.8.0',
     'python-rapidjson~=0.6.0',
     'logstats~=0.2.1',
@@ -106,7 +106,7 @@ setup(
         "query functionality, decentralized control, immutable data storage and "
         "built-in asset support, BigchainDB is like a database with blockchain "
         "characteristics."
-        ),
+    ),
     url='https://github.com/BigchainDB/bigchaindb/',
     author='BigchainDB Contributors',
     author_email='devs@bigchaindb.com',
@@ -130,7 +130,7 @@ setup(
 
     packages=find_packages(exclude=['tests*']),
 
-    scripts = ['pkg/scripts/bigchaindb-monit-config'],
+    scripts=['pkg/scripts/bigchaindb-monit-config'],
 
     entry_points={
         'console_scripts': [