diff --git a/matrix_client/api.py b/matrix_client/api.py
index 264861c2..a6634d17 100644
--- a/matrix_client/api.py
+++ b/matrix_client/api.py
@@ -152,7 +152,8 @@ def login(self, login_type, **kwargs):
             "type": login_type
         }
         for key in kwargs:
-            content[key] = kwargs[key]
+            if kwargs[key]:
+                content[key] = kwargs[key]
 
         return self._send("POST", "/login", content)
 
diff --git a/matrix_client/client.py b/matrix_client/client.py
index be1abe74..d9a59d52 100644
--- a/matrix_client/client.py
+++ b/matrix_client/client.py
@@ -208,9 +208,10 @@ def _post_registration(self, response):
         self._sync()
         return self.token
 
-    # TODO: combine login methods into single method controlled by kwargs
     def login_with_password_no_sync(self, username, password):
-        """ Login to the homeserver.
+        """Deprecated. Use ``login`` with ``sync=False`` instead.
+
+        Login to the homeserver.
 
         Args:
             username (str): Account username
@@ -222,17 +223,15 @@ def login_with_password_no_sync(self, username, password):
         Raises:
             MatrixRequestError
         """
-        response = self.api.login(
-            "m.login.password", user=username, password=password
-        )
-        self.user_id = response["user_id"]
-        self.token = response["access_token"]
-        self.hs = response["home_server"]
-        self.api.token = self.token
-        return self.token
+        warn("login_with_password_no_sync is deprecated. Use login with sync=False"
+             "instead.",
+             DeprecationWarning)
+        return self.login(username, password, sync=False)
 
     def login_with_password(self, username, password, limit=10):
-        """ Login to the homeserver.
+        """Deprecated. Use ``login`` with ``sync=True`` instead.
+
+        Login to the homeserver.
 
         Args:
             username (str): Account username
@@ -246,12 +245,41 @@ def login_with_password(self, username, password, limit=10):
         Raises:
             MatrixRequestError
         """
-        token = self.login_with_password_no_sync(username, password)
+        warn("login_with_password is deprecated. Use login with sync=True instead.",
+             DeprecationWarning)
+        return self.login(username, password, limit, sync=True)
 
-        """ Limit Filter """
-        self.sync_filter = '{ "room": { "timeline" : { "limit" : %i } } }' % limit
-        self._sync()
-        return token
+    def login(self, username, password, limit=10, sync=True, device_id=None):
+        """Login to the homeserver.
+
+        Args:
+            username (str): Account username
+            password (str): Account password
+            limit (int): Deprecated. How many messages to return when syncing.
+                This will be replaced by a filter API in a later release.
+            sync (bool): Optional. Whether to initiate a /sync request after logging in.
+            device_id (str): Optional. ID of the client device. The server will
+                auto-generate a device_id if this is not specified.
+
+        Returns:
+            str: Access token
+
+        Raises:
+            MatrixRequestError
+        """
+        response = self.api.login(
+            "m.login.password", user=username, password=password, device_id=device_id
+        )
+        self.user_id = response["user_id"]
+        self.token = response["access_token"]
+        self.hs = response["home_server"]
+        self.api.token = self.token
+
+        if sync:
+            """ Limit Filter """
+            self.sync_filter = '{ "room": { "timeline" : { "limit" : %i } } }' % limit
+            self._sync()
+        return self.token
 
     def logout(self):
         """ Logout from the homeserver.