diff --git a/app/devices/__init__.py b/app/devices/__init__.py
index ece082e..1280c28 100644
--- a/app/devices/__init__.py
+++ b/app/devices/__init__.py
@@ -63,11 +63,7 @@ def get_device(device_id):
     :type device_id: int
     :returns: Requested device
     :rtype: Device
-    :raises: ValueError if device does not exist
     """
-    if not Device.exists(id=device_id):
-        raise ValueError("Device with id %s does not exist" % device_id)
-
     return Device.get(id=device_id)
 
 
@@ -79,23 +75,14 @@ def get_device_type(device_type_id):
     :type device_type_id: int
     :returns: Requested device type
     :rtype: DeviceType
-    :raises: ValueError if device type does not exist
     """
-    if not DeviceType.exists(id=device_type_id):
-        raise ValueError("Device type with id %s does not exist" %
-                         device_type_id)
-
     return DeviceType.get(id=device_type_id)
 
 
 def delete_device(device_id):
     """
     Tries to delete device with given parameters. Does not raise errors
-
     """
-    if not Device.exists(id=device_id):
-        return
-
     Device.get(id=device_id).delete()
 
 
diff --git a/app/devices/models.py b/app/devices/models.py
index 07b4bbf..88a5632 100644
--- a/app/devices/models.py
+++ b/app/devices/models.py
@@ -76,7 +76,7 @@ class Recording(db.Model):
          * raw_record (useless)
 
         """
-        return Recording.query.filter_by(**kwargs).first()
+        return Recording.query.filter_by(**kwargs).first_or_404()
 
     def __repr__(self):
         return '<Recording (value=%s, recorded_at=%s)>' % (
@@ -163,7 +163,7 @@ class Device(db.Model):
          * configuration (useless)
 
         """
-        return Device.query.filter_by(**kwargs).first()
+        return Device.query.filter_by(**kwargs).first_or_404()
 
     @staticmethod
     def exists(**kwargs):
@@ -271,7 +271,7 @@ class DeviceType(db.Model):
          * id
          * name
         """
-        return DeviceType.query.filter_by(**kwargs).first()
+        return DeviceType.query.filter_by(**kwargs).first_or_404()
 
     @staticmethod
     def exists(**kwargs):
diff --git a/app/mqtt/mqtt_client.py b/app/mqtt/mqtt_client.py
index a722fbe..fbf9682 100644
--- a/app/mqtt/mqtt_client.py
+++ b/app/mqtt/mqtt_client.py
@@ -59,7 +59,7 @@ class MqttClient:
             return
 
     @staticmethod
-    def get_device_id(topic) -> int:
+    def get_device_id(topic):
         device_token, device_id = topic.split("/")
         if device_token == "device":
             return int(device_id)