diff --git a/app/admin.py b/app/admin.py
index 819b99d..7712358 100644
--- a/app/admin.py
+++ b/app/admin.py
@@ -1,12 +1,14 @@
 import flask_login as login
+from flask import Flask
 from flask_admin import Admin
 from flask_admin.contrib.sqla import ModelView
+from flask_sqlalchemy import SQLAlchemy
 
 from models import Location, Order, OrderItem, Product, User
 
 
 class ModelBaseView(ModelView):
-    def is_accessible(self):
+    def is_accessible(self) -> bool:
         if login.current_user.is_anonymous():
             return False
 
@@ -29,7 +31,7 @@ class LocationAdminModel(ModelBaseView):
     form_columns = ("name", "address", "website", "telephone")
 
 
-def init_admin(app, db):
+def init_admin(app: Flask, db: SQLAlchemy) -> None:
     admin = Admin(app, name="Haldis", url="/admin", template_mode="bootstrap3")
 
     admin.add_view(UserAdminModel(User, db.session))
diff --git a/app/app.py b/app/app.py
index e1674d5..8e6c063 100644
--- a/app/app.py
+++ b/app/app.py
@@ -1,4 +1,5 @@
 import logging
+import typing
 from datetime import datetime
 from logging.handlers import TimedRotatingFileHandler
 
@@ -19,7 +20,7 @@ from utils import euro_string
 from zeus import init_oauth
 
 
-def create_app():
+def create_app() -> Manager:
     app = Flask(__name__)
 
     # Load the config file
@@ -34,7 +35,7 @@ def create_app():
     return manager
 
 
-def register_plugins(app, debug: bool):
+def register_plugins(app: Flask, debug: bool) -> Manager:
     # Register Airbrake and enable the logrotation
     if not app.debug:
         timedFileHandler = TimedRotatingFileHandler(
@@ -96,17 +97,17 @@ def register_plugins(app, debug: bool):
     return manager
 
 
-def add_handlers(app):
+def add_handlers(app: Flask) -> None:
     @app.errorhandler(404)
-    def handle404(e):
+    def handle404(e) -> typing.Tuple[str, int]:
         return render_template("errors/404.html"), 404
 
     @app.errorhandler(401)
-    def handle401(e):
+    def handle401(e) -> typing.Tuple[str, int]:
         return render_template("errors/401.html"), 401
 
 
-def add_routes(application):
+def add_routes(application: Flask) -> None:
     # import views  # TODO convert to blueprint
     # import views.stats  # TODO convert to blueprint
 
@@ -127,9 +128,9 @@ def add_routes(application):
         application.register_blueprint(debug_bp, url_prefix="/debug")
 
 
-def add_template_filters(app):
+def add_template_filters(app: Flask) -> None:
     @app.template_filter("countdown")
-    def countdown(value, only_positive=True, show_text=True):
+    def countdown(value, only_positive: bool = True, show_text: bool = True) -> str:
         delta = value - datetime.now()
         if delta.total_seconds() < 0 and only_positive:
             return "closed"
@@ -141,11 +142,11 @@ def add_template_filters(app):
         return time
 
     @app.template_filter("year")
-    def current_year(value):
+    def current_year(value: typing.Any) -> str:
         return str(datetime.now().year)
 
     @app.template_filter("euro")
-    def euro(value):
+    def euro(value: int) -> None:
         euro_string(value)
 
 
diff --git a/app/fatmodels.py b/app/fatmodels.py
index f4c4c53..79eac01 100644
--- a/app/fatmodels.py
+++ b/app/fatmodels.py
@@ -1,3 +1,5 @@
+import typing
+
 from sqlalchemy.sql import desc, func
 
 from models import Location, Order, OrderItem, Product, User
@@ -42,7 +44,7 @@ class FatOrderItem(OrderItem, FatModel):
 
 class FatProduct(Product, FatModel):
     @classmethod
-    def top4(cls):
+    def top4(cls) -> None:
         top4 = (
             OrderItem.query.join(Product)
             .join(Location)
diff --git a/app/forms.py b/app/forms.py
index a41c188..4003944 100644
--- a/app/forms.py
+++ b/app/forms.py
@@ -3,7 +3,8 @@ from datetime import datetime, timedelta
 from flask import session
 from flask_login import current_user
 from flask_wtf import FlaskForm as Form
-from wtforms import DateTimeField, SelectField, StringField, SubmitField, validators
+from wtforms import (DateTimeField, SelectField, StringField, SubmitField,
+                     validators)
 
 from models import Location, User
 from utils import euro_string
@@ -20,7 +21,7 @@ class OrderForm(Form):
     stoptime = DateTimeField("Stoptime", format="%d-%m-%Y %H:%M")
     submit_button = SubmitField("Submit")
 
-    def populate(self):
+    def populate(self) -> None:
         if current_user.is_admin():
             self.courrier_id.choices = [(0, None)] + [
                 (u.id, u.username) for u in User.query.order_by("username")
@@ -42,7 +43,7 @@ class OrderItemForm(Form):
     extra = StringField("Extra")
     submit_button = SubmitField("Submit")
 
-    def populate(self, location):
+    def populate(self, location: Location) -> None:
         self.product_id.choices = [
             (i.id, (i.name + ": " + euro_string(i.price))) for i in location.products
         ]
@@ -51,12 +52,12 @@ class OrderItemForm(Form):
 class AnonOrderItemForm(OrderItemForm):
     name = StringField("Name", validators=[validators.required()])
 
-    def populate(self, location):
+    def populate(self, location: Location) -> None:
         OrderItemForm.populate(self, location)
         if self.name.data is None:
             self.name.data = session.get("anon_name", None)
 
-    def validate(self):
+    def validate(self) -> bool:
         rv = OrderForm.validate(self)
         if not rv:
             return False
diff --git a/app/login.py b/app/login.py
index 27c2e8a..c50b245 100644
--- a/app/login.py
+++ b/app/login.py
@@ -1,6 +1,6 @@
-from flask import abort, Blueprint
-from flask import redirect, session, url_for
+from flask import Blueprint, abort, redirect, session, url_for
 from flask_login import current_user, logout_user
+from werkzeug.wrappers import Response
 
 from models import User
 from zeus import zeus_login
@@ -8,9 +8,9 @@ from zeus import zeus_login
 auth_bp = Blueprint("auth_bp", __name__)
 
 
-def init_login(app):
+def init_login(app) -> None:
     @app.login_manager.user_loader
-    def load_user(userid):
+    def load_user(userid) -> User:
         return User.query.filter_by(id=userid).first()
 
 
@@ -20,13 +20,13 @@ def login():
 
 
 @auth_bp.route("/logout")
-def logout():
+def logout() -> Response:
     if "zeus_token" in session:
         session.pop("zeus_token", None)
     logout_user()
     return redirect(url_for("general_bp.home"))
 
 
-def before_request():
+def before_request() -> None:
     if current_user.is_anonymous() or not current_user.is_allowed():
         abort(401)
diff --git a/app/notification.py b/app/notification.py
index 2fc8cbc..be20c3c 100644
--- a/app/notification.py
+++ b/app/notification.py
@@ -7,7 +7,7 @@ from flask import current_app as app
 from flask import url_for
 
 
-def post_order_to_webhook(order_item):
+def post_order_to_webhook(order_item) -> None:
     message = ""
     if order_item.courrier is not None:
         message = "<!channel|@channel> {3} is going to {1}, order <{0}|here>! Deadline in {2} minutes!".format(
@@ -27,14 +27,14 @@ def post_order_to_webhook(order_item):
 
 
 class WebhookSenderThread(Thread):
-    def __init__(self, message):
+    def __init__(self, message: str) -> None:
         super(WebhookSenderThread, self).__init__()
         self.message = message
 
-    def run(self):
+    def run(self) -> None:
         self.slack_webhook()
 
-    def slack_webhook(self):
+    def slack_webhook(self) -> None:
         js = json.dumps({"text": self.message})
         url = app.config["SLACK_WEBHOOK"]
         if len(url) > 0:
@@ -43,7 +43,7 @@ class WebhookSenderThread(Thread):
             app.logger.info(str(js))
 
 
-def remaining_minutes(value):
+def remaining_minutes(value) -> str:
     delta = value - datetime.now()
     if delta.total_seconds() < 0:
         return "0"
diff --git a/app/utils.py b/app/utils.py
index 0c456ce..1584117 100644
--- a/app/utils.py
+++ b/app/utils.py
@@ -1,4 +1,4 @@
-def euro_string(value):
+def euro_string(value: int) -> str:
     """
     Convert cents to string formatted euro
     """
diff --git a/app/zeus.py b/app/zeus.py
index b56f70a..8ca77d1 100644
--- a/app/zeus.py
+++ b/app/zeus.py
@@ -1,6 +1,10 @@
-from flask import current_app, flash, redirect, request, session, url_for, Blueprint
+import typing
+
+from flask import (Blueprint, current_app, flash, redirect, request, session,
+                   url_for)
 from flask_login import login_user
-from flask_oauthlib.client import OAuthException, OAuth
+from flask_oauthlib.client import OAuth, OAuthException
+from werkzeug.wrappers import Response
 
 from models import User, db
 
@@ -14,7 +18,9 @@ def zeus_login():
 
 
 @oauth_bp.route("/login/zeus/authorized")
-def authorized():
+def authorized() -> typing.Any:
+    # type is 'typing.Union[str, Response]', but this errors due to
+    #   https://github.com/python/mypy/issues/7187
     resp = current_app.zeus.authorized_response()
     if resp is None:
         return "Access denied: reason=%s error=%s" % (
@@ -60,12 +66,12 @@ def init_oauth(app):
     return zeus
 
 
-def login_and_redirect_user(user):
+def login_and_redirect_user(user) -> Response:
     login_user(user)
     return redirect(url_for("general_bp.home"))
 
 
-def create_user(username):
+def create_user(username) -> User:
     user = User()
     user.configure(username, False, 1)
     db.session.add(user)