diff --git a/mypy.ini b/mypy.ini
index 61406f0331..af039c135f 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -315,8 +315,6 @@ strict_optional = False
 strict_optional = False
 [mypy-zerver.views.messages]  # Other issues in this file too
 strict_optional = False
-[mypy-zerver.views.users]  # Other issues in this file too
-strict_optional = False
 
 # One change required?
 
diff --git a/zerver/lib/actions.py b/zerver/lib/actions.py
index 13cb86745a..d1af86015c 100644
--- a/zerver/lib/actions.py
+++ b/zerver/lib/actions.py
@@ -483,7 +483,7 @@ def do_create_user(email: str, password: Optional[str], realm: Realm, full_name:
                    timezone: str="", avatar_source: str=UserProfile.AVATAR_FROM_GRAVATAR,
                    default_sending_stream: Optional[Stream]=None,
                    default_events_register_stream: Optional[Stream]=None,
-                   default_all_public_streams: bool=None,
+                   default_all_public_streams: Optional[bool]=None,
                    prereg_user: Optional[PreregistrationUser]=None,
                    newsletter_data: Optional[Dict[str, str]]=None,
                    default_stream_groups: List[DefaultStreamGroup]=[],
diff --git a/zerver/lib/users.py b/zerver/lib/users.py
index 667bef5a41..a383d9d889 100644
--- a/zerver/lib/users.py
+++ b/zerver/lib/users.py
@@ -67,7 +67,7 @@ def check_valid_bot_type(user_profile: UserProfile, bot_type: int) -> None:
     if bot_type not in user_profile.allowed_bot_types:
         raise JsonableError(_('Invalid bot type'))
 
-def check_valid_interface_type(interface_type: int) -> None:
+def check_valid_interface_type(interface_type: Optional[int]) -> None:
     if interface_type not in Service.ALLOWED_INTERFACE_TYPES:
         raise JsonableError(_('Invalid interface type'))
 
diff --git a/zerver/views/users.py b/zerver/views/users.py
index 4574f57061..c2aa11919e 100644
--- a/zerver/views/users.py
+++ b/zerver/views/users.py
@@ -141,6 +141,7 @@ def avatar(request: HttpRequest, email_or_id: str, medium: bool=False) -> HttpRe
     # our templates depend on being able to use the ampersand to
     # add query parameters to our url, get_avatar_url does '?x=x'
     # hacks to prevent us from having to jump through decode/encode hoops.
+    assert url is not None
     assert '?' in url
     url += '&' + request.META['QUERY_STRING']
     return redirect(url)
@@ -198,6 +199,7 @@ def patch_bot_backend(
 
     if service_payload_url is not None:
         check_valid_interface_type(service_interface)
+        assert service_interface is not None
         do_update_outgoing_webhook_service(bot, service_interface, service_payload_url)
 
     if config_data is not None: