diff --git a/zulip/integrations/codebase/zulip_codebase_mirror b/zulip/integrations/codebase/zulip_codebase_mirror
index c109f15..ed7ade2 100755
--- a/zulip/integrations/codebase/zulip_codebase_mirror
+++ b/zulip/integrations/codebase/zulip_codebase_mirror
@@ -286,10 +286,10 @@ def run_mirror():
     try:
         sleepInterval = 1
         while True:
-            events = make_api_call("activity")[::-1]
+            events = make_api_call("activity")
             if events is not None:
                 sleepInterval = 1
-                for event in events:
+                for event in events[::-1]:
                     timestamp = event.get('event', {}).get('timestamp', '')
                     event_date = dateutil.parser.parse(timestamp)
                     if event_date > since:
diff --git a/zulip/integrations/git/zulip_git_config.py b/zulip/integrations/git/zulip_git_config.py
index 4f49297..6ba36b8 100644
--- a/zulip/integrations/git/zulip_git_config.py
+++ b/zulip/integrations/git/zulip_git_config.py
@@ -20,7 +20,7 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
-from typing import Dict, Text
+from typing import Dict, Text, Optional
 
 # Change these values to configure authentication for the plugin
 ZULIP_USER = "git-bot@example.com"
@@ -42,7 +42,7 @@ ZULIP_API_KEY = "0123456789abcdef0123456789abcdef"
 # * topic "master"
 # And similarly for branch "test-post-receive" (for use when testing).
 def commit_notice_destination(repo, branch, commit):
-    # type: (Text, Text, Text) -> Dict[Text, Text]
+    # type: (Text, Text, Text) -> Optional[Dict[Text, Text]]
     if branch in ["master", "test-post-receive"]:
         return dict(stream  = "commits",
                     subject = u"%s" % (branch,))
diff --git a/zulip/integrations/google/get-google-credentials b/zulip/integrations/google/get-google-credentials
index e919388..8b70248 100644
--- a/zulip/integrations/google/get-google-credentials
+++ b/zulip/integrations/google/get-google-credentials
@@ -8,9 +8,11 @@ from oauth2client import client
 from oauth2client import tools
 from oauth2client.file import Storage
 
+from typing import Optional
+
 try:
     import argparse
-    flags = argparse.ArgumentParser(parents=[tools.argparser]).parse_args()
+    flags = argparse.ArgumentParser(parents=[tools.argparser]).parse_args()  # type: Optional[argparse.Namespace]
 except ImportError:
     flags = None
 
diff --git a/zulip/integrations/openshift/zulip_openshift_config.py b/zulip/integrations/openshift/zulip_openshift_config.py
index 9f4296d..faebbf3 100755
--- a/zulip/integrations/openshift/zulip_openshift_config.py
+++ b/zulip/integrations/openshift/zulip_openshift_config.py
@@ -21,7 +21,7 @@
 # THE SOFTWARE.
 
 # https://github.com/python/mypy/issues/1141
-from typing import Dict, Text
+from typing import Dict, Text, Optional
 
 # Change these values to configure authentication for the plugin
 ZULIP_USER = 'openshift-bot@example.com'
@@ -42,7 +42,7 @@ ZULIP_API_KEY = '0123456789abcdef0123456789abcdef'
 # * topic "master"
 # And similarly for branch "test-post-receive" (for use when testing).
 def deployment_notice_destination(branch):
-    # type: (str) -> Dict[str, Text]
+    # type: (str) -> Optional[Dict[str, Text]]
     if branch in ['master', 'test-post-receive']:
         return dict(stream  = 'deployments',
                     subject = u'%s' % (branch,))
@@ -69,7 +69,7 @@ def format_deployment_message(
 
 ## If properly installed, the Zulip API should be in your import
 ## path, but if not, set a custom path below
-ZULIP_API_PATH = None  # type: str
+ZULIP_API_PATH = None  # type: Optional[str]
 
 # Set this to your Zulip server's API URI
 ZULIP_SITE = 'https://zulip.example.com'
diff --git a/zulip/integrations/zephyr/sync-public-streams b/zulip/integrations/zephyr/sync-public-streams
index 26fad9b..1ead1c5 100755
--- a/zulip/integrations/zephyr/sync-public-streams
+++ b/zulip/integrations/zephyr/sync-public-streams
@@ -11,10 +11,10 @@ import unicodedata
 sys.path.append(os.path.join(os.path.dirname(__file__), '..', 'api'))
 import zulip
 
-from typing import Set
+from typing import Set, Optional
 
 def fetch_public_streams():
-    # type: () -> Set[bytes]
+    # type: () -> Optional[Set[bytes]]
     public_streams = set()
 
     try:
diff --git a/zulip/integrations/zephyr/zephyr_mirror_backend.py b/zulip/integrations/zephyr/zephyr_mirror_backend.py
index 77f495f..8abe066 100755
--- a/zulip/integrations/zephyr/zephyr_mirror_backend.py
+++ b/zulip/integrations/zephyr/zephyr_mirror_backend.py
@@ -21,7 +21,7 @@
 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 from __future__ import absolute_import
-from typing import IO, Any, Dict, List, Text, Union, Set, Tuple
+from typing import IO, Any, Dict, List, Text, Union, Set, Tuple, Optional
 from types import FrameType
 
 import sys
@@ -309,7 +309,7 @@ def parse_zephyr_body(zephyr_data, notice_format):
     return (zsig, body)
 
 def parse_crypt_table(zephyr_class, instance):
-    # type: (Text, str) -> str
+    # type: (Text, str) -> Optional[str]
     try:
         crypt_table = open(os.path.join(os.environ["HOME"], ".crypt-table"))
     except IOError:
@@ -604,7 +604,7 @@ def send_unauthed_zephyr(zwrite_args, content):
     return send_zephyr(zwrite_args + ["-d"], content)
 
 def zcrypt_encrypt_content(zephyr_class, instance, content):
-    # type: (str, str, str) -> str
+    # type: (str, str, str) -> Optional[str]
     keypath = parse_crypt_table(zephyr_class, instance)
     if keypath is None:
         return None