diff --git a/homeassistant/components/knx/__init__.py b/homeassistant/components/knx/__init__.py
index 1910227a5a4d77..fa014335df97f5 100644
--- a/homeassistant/components/knx/__init__.py
+++ b/homeassistant/components/knx/__init__.py
@@ -247,7 +247,7 @@ async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
                 create_knx_exposure(hass, knx_module.xknx, expose_config)
             )
 
-    hass.config_entries.async_setup_platforms(
+    await hass.config_entries.async_forward_entry_setups(
         entry,
         [
             platform
diff --git a/tests/components/knx/conftest.py b/tests/components/knx/conftest.py
index e5cf18b0c3c691..23e04b672ba73c 100644
--- a/tests/components/knx/conftest.py
+++ b/tests/components/knx/conftest.py
@@ -55,16 +55,21 @@ def assert_state(self, entity_id: str, state: str, **attributes) -> None:
     async def setup_integration(self, config):
         """Create the KNX integration."""
 
-        def disable_rate_limiter():
-            """Disable rate limiter for tests."""
+        async def patch_xknx_start():
+            """Patch `xknx.start` for unittests."""
             # after XKNX.__init__() to not overwrite it by the config entry again
             # before StateUpdater starts to avoid slow down of tests
             self.xknx.rate_limit = 0
+            # set XknxConnectionState.CONNECTED to avoid `unavailable` entities at startup
+            # and start StateUpdater. This would be awaited on normal startup too.
+            await self.xknx.connection_manager.connection_state_changed(
+                XknxConnectionState.CONNECTED
+            )
 
         def knx_ip_interface_mock():
             """Create a xknx knx ip interface mock."""
             mock = Mock()
-            mock.start = AsyncMock(side_effect=disable_rate_limiter)
+            mock.start = AsyncMock(side_effect=patch_xknx_start)
             mock.stop = AsyncMock()
             mock.send_telegram = AsyncMock(side_effect=self._outgoing_telegrams.put)
             return mock
@@ -81,9 +86,6 @@ def fish_xknx(*args, **kwargs):
         ):
             self.mock_config_entry.add_to_hass(self.hass)
             await async_setup_component(self.hass, KNX_DOMAIN, {KNX_DOMAIN: config})
-            await self.xknx.connection_manager.connection_state_changed(
-                XknxConnectionState.CONNECTED
-            )
             await self.hass.async_block_till_done()
 
     ########################