diff --git a/.strict-typing b/.strict-typing
index a565e04e3e5..0cbb1aa92e9 100644
--- a/.strict-typing
+++ b/.strict-typing
@@ -81,6 +81,7 @@ homeassistant.components.cpuspeed.*
 homeassistant.components.deconz.*
 homeassistant.components.device_automation.*
 homeassistant.components.device_tracker.*
+homeassistant.components.demo.*
 homeassistant.components.devolo_home_control.*
 homeassistant.components.devolo_home_network.*
 homeassistant.components.dhcp.*
diff --git a/homeassistant/components/demo/alarm_control_panel.py b/homeassistant/components/demo/alarm_control_panel.py
index b73e5444b22..3a94aaa7c29 100644
--- a/homeassistant/components/demo/alarm_control_panel.py
+++ b/homeassistant/components/demo/alarm_control_panel.py
@@ -31,7 +31,7 @@ async def async_setup_platform(
     """Set up the Demo alarm control panel platform."""
     async_add_entities(
         [
-            ManualAlarm(
+            ManualAlarm(  # type:ignore[no-untyped-call]
                 hass,
                 "Security",
                 "1234",
diff --git a/homeassistant/components/demo/mailbox.py b/homeassistant/components/demo/mailbox.py
index 8a7df70df80..6f0b23525e5 100644
--- a/homeassistant/components/demo/mailbox.py
+++ b/homeassistant/components/demo/mailbox.py
@@ -76,7 +76,7 @@ class DemoMailbox(Mailbox):
         """Return a list of the current messages."""
         return sorted(
             self._messages.values(),
-            key=lambda item: item["info"]["origtime"],
+            key=lambda item: item["info"]["origtime"],  # type: ignore[no-any-return]
             reverse=True,
         )
 
diff --git a/mypy.ini b/mypy.ini
index 3c886bdc1c2..1218992ab3a 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -569,6 +569,16 @@ disallow_untyped_defs = true
 warn_return_any = true
 warn_unreachable = true
 
+[mypy-homeassistant.components.demo.*]
+check_untyped_defs = true
+disallow_incomplete_defs = true
+disallow_subclassing_any = true
+disallow_untyped_calls = true
+disallow_untyped_decorators = true
+disallow_untyped_defs = true
+warn_return_any = true
+warn_unreachable = true
+
 [mypy-homeassistant.components.devolo_home_control.*]
 check_untyped_defs = true
 disallow_incomplete_defs = true