diff --git a/requirements.txt b/requirements.txt
index 379fcd2..8c2c46c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -10,5 +10,8 @@ pytest-cov
 -e ./zulip_bots
 -e ./zulip_botserver
 -e git+https://github.com/zulip/zulint@14e3974001bf8442a6a3486125865660f1f2eb68#egg=zulint==1.0.0
-mypy==0.812
+mypy==0.910
+types-python-dateutil
+types-pytz
+types-requests
 gitlint>=0.13.0
diff --git a/zulip/tests/__init__.py b/zulip/tests/__init__.py
index f1e69a3..84a60e8 100644
--- a/zulip/tests/__init__.py
+++ b/zulip/tests/__init__.py
@@ -1,4 +1,4 @@
 import pkgutil
-from typing import Iterable
+from typing import List
 
-__path__ = pkgutil.extend_path(__path__, __name__)  # type: Iterable[str]
+__path__ = pkgutil.extend_path(__path__, __name__)  # type: List[str]
diff --git a/zulip_bots/zulip_bots/bots/witai/witai.py b/zulip_bots/zulip_bots/bots/witai/witai.py
index 1adb950..46de582 100644
--- a/zulip_bots/zulip_bots/bots/witai/witai.py
+++ b/zulip_bots/zulip_bots/bots/witai/witai.py
@@ -80,6 +80,8 @@ def get_handle(location: str) -> Optional[Callable[[Dict[str, Any]], Optional[st
     """
     try:
         spec = importlib.util.spec_from_file_location("module.name", location)
+        if spec is None:
+            return None
         handler = importlib.util.module_from_spec(spec)
         loader = spec.loader
         if not isinstance(loader, importlib.abc.Loader):
diff --git a/zulip_bots/zulip_bots/finder.py b/zulip_bots/zulip_bots/finder.py
index 0f8ee88..8462a1c 100644
--- a/zulip_bots/zulip_bots/finder.py
+++ b/zulip_bots/zulip_bots/finder.py
@@ -13,6 +13,8 @@ import importlib_metadata as metadata
 
 def import_module_from_source(path: str, name: str) -> Any:
     spec = importlib.util.spec_from_file_location(name, path)
+    if spec is None:
+        return None
     module = importlib.util.module_from_spec(spec)
     loader = spec.loader
     if not isinstance(loader, importlib.abc.Loader):
diff --git a/zulip_botserver/tests/__init__.py b/zulip_botserver/tests/__init__.py
index f1e69a3..84a60e8 100644
--- a/zulip_botserver/tests/__init__.py
+++ b/zulip_botserver/tests/__init__.py
@@ -1,4 +1,4 @@
 import pkgutil
-from typing import Iterable
+from typing import List
 
-__path__ = pkgutil.extend_path(__path__, __name__)  # type: Iterable[str]
+__path__ = pkgutil.extend_path(__path__, __name__)  # type: List[str]