diff --git a/bots/jabber_mirror_backend.py b/bots/jabber_mirror_backend.py
index 36515d5..7fde854 100755
--- a/bots/jabber_mirror_backend.py
+++ b/bots/jabber_mirror_backend.py
@@ -44,26 +44,32 @@ import threading
 import optparse
 
 from sleekxmpp import ClientXMPP, InvalidJID, JID
+from sleekxmpp.stanza import Message as JabberMessage
 from sleekxmpp.exceptions import IqError, IqTimeout
 from six.moves.configparser import SafeConfigParser
 import os, sys, zulip, getpass
 import re
+from typing import Any, Callable
 
 __version__ = "1.1"
 
 def room_to_stream(room):
+    # type: (str) -> str
     return room + "/xmpp"
 
 def stream_to_room(stream):
+    # type: (str) -> str
     return stream.lower().rpartition("/xmpp")[0]
 
 def jid_to_zulip(jid):
+    # type: (JID) -> str
     suffix = ''
     if not jid.username.endswith("-bot"):
         suffix = options.zulip_email_suffix
     return "%s%s@%s" % (jid.username, suffix, options.zulip_domain)
 
 def zulip_to_jid(email, jabber_domain):
+    # type: (str, str) -> JID
     jid = JID(email, domain=jabber_domain)
     if (options.zulip_email_suffix
         and options.zulip_email_suffix in jid.username
@@ -73,6 +79,7 @@ def zulip_to_jid(email, jabber_domain):
 
 class JabberToZulipBot(ClientXMPP):
     def __init__(self, jid, password, rooms):
+        # type: (JID, str, List[str]) -> None
         if jid.resource:
             self.nick = jid.resource
         else:
@@ -90,15 +97,18 @@ class JabberToZulipBot(ClientXMPP):
         self.register_plugin('xep_0199') # XMPP Ping
 
     def set_zulip_client(self, client):
+        # type: (zulip.Client) -> None
         self.zulip = client
 
     def session_start(self, event):
+        # type: (Dict[str, Any]) -> None
         self.get_roster()
         self.send_presence()
         for room in self.rooms_to_join:
             self.join_muc(room)
 
     def join_muc(self, room):
+        # type: (str) -> None
         if room in self.rooms:
             return
         logging.debug("Joining " + room)
@@ -124,6 +134,7 @@ class JabberToZulipBot(ClientXMPP):
             logging.error("Could not configure room: " + str(muc_jid))
 
     def leave_muc(self, room):
+        # type: (str) -> None
         if room not in self.rooms:
             return
         logging.debug("Leaving " + room)
@@ -132,6 +143,7 @@ class JabberToZulipBot(ClientXMPP):
         self.plugin['xep_0045'].leaveMUC(muc_jid, self.nick)
 
     def message(self, msg):
+        # type: (JabberMessage) -> Any
         try:
             if msg["type"] == "groupchat":
                 return self.group(msg)
@@ -144,6 +156,7 @@ class JabberToZulipBot(ClientXMPP):
             logging.exception("Error forwarding Jabber => Zulip")
 
     def private(self, msg):
+        # type: (JabberMessage) -> None
         if options.mode == 'public' or msg['thread'] == u'\u1FFFE':
             return
         sender = jid_to_zulip(msg["from"])
@@ -160,6 +173,7 @@ class JabberToZulipBot(ClientXMPP):
             logging.error(ret)
 
     def group(self, msg):
+        # type: (JabberMessage) -> None
         if options.mode == 'personal' or msg["thread"] == u'\u1FFFE':
             return
 
@@ -187,6 +201,7 @@ class JabberToZulipBot(ClientXMPP):
             logging.error(ret)
 
     def nickname_to_jid(self, room, nick):
+        # type: (str, str) -> JID
         jid = self.plugin['xep_0045'].getJidProperty(room, nick, "jid")
         if (jid is None or jid == ''):
             return JID(local=nick.replace(' ', ''), domain=self.boundjid.domain)
@@ -195,13 +210,16 @@ class JabberToZulipBot(ClientXMPP):
 
 class ZulipToJabberBot(object):
     def __init__(self, zulip_client):
+        # type: (zulip.Client) -> None
         self.client = zulip_client
         self.jabber = None # type: JabberToZulipBot
 
     def set_jabber_client(self, client):
+        # type: (JabberToZulipBot) -> None
         self.jabber = client
 
     def process_event(self, event):
+        # type: (Dict[str, Any]) -> None
         if event['type'] == 'message':
             message = event["message"]
             if message['sender_email'] != self.client.email:
@@ -220,6 +238,7 @@ class ZulipToJabberBot(object):
             self.process_stream(event)
 
     def stream_message(self, msg):
+        # type: (Dict[str, str]) -> None
         stream = msg['display_recipient']
         if not stream.endswith("/xmpp"):
             return
@@ -234,6 +253,7 @@ class ZulipToJabberBot(object):
         outgoing.send()
 
     def private_message(self, msg):
+        # type: (Dict[str, Any]) -> None
         for recipient in msg['display_recipient']:
             if recipient["email"] == self.client.email:
                 continue
@@ -249,6 +269,7 @@ class ZulipToJabberBot(object):
             outgoing.send()
 
     def process_subscription(self, event):
+        # type: (Dict[str, Any]) -> None
         if event['op'] == 'add':
             streams = [s['name'].lower() for s in event['subscriptions']]
             streams = [s for s in streams if s.endswith("/xmpp")]
@@ -261,6 +282,7 @@ class ZulipToJabberBot(object):
                 self.jabber.leave_muc(stream_to_room(stream))
 
     def process_stream(self, event):
+        # type: (Dict[str, Any]) -> None
         if event['op'] == 'occupy':
             streams = [s['name'].lower() for s in event['streams']]
             streams = [s for s in streams if s.endswith("/xmpp")]
@@ -273,7 +295,9 @@ class ZulipToJabberBot(object):
                 self.jabber.leave_muc(stream_to_room(stream))
 
 def get_rooms(zulip):
+    # type: (zulip) -> List[str]
     def get_stream_infos(key, method):
+        # type: (str, Callable) -> Any
         ret = method()
         if ret.get("result") != "success":
             logging.error(ret)
@@ -285,7 +309,7 @@ def get_rooms(zulip):
     else:
         stream_infos = get_stream_infos("subscriptions", zulip.client.list_subscriptions)
 
-    rooms = []
+    rooms = [] # type: List[str]
     for stream_info in stream_infos:
             stream = stream_info['name']
             if stream.endswith("/xmpp"):
@@ -293,6 +317,7 @@ def get_rooms(zulip):
     return rooms
 
 def config_error(msg):
+    # type: (str) -> None
     sys.stderr.write("%s\n" % (msg,))
     sys.exit(2)