diff --git a/homeassistant/components/yeelight/light.py b/homeassistant/components/yeelight/light.py
index 5bf123414b78..0464eba2b291 100644
--- a/homeassistant/components/yeelight/light.py
+++ b/homeassistant/components/yeelight/light.py
@@ -742,7 +742,7 @@ class YeelightBaseLight(YeelightEntity, LightEntity):
         """Activate flash."""
         if not flash:
             return
-        if int(self._get_property("color_mode")) != 1 or not self.hs_color:
+        if self.color_mode is not ColorMode.RGB or not self.hs_color:
             _LOGGER.error("Flash supported currently only in RGB mode")
             return
 
@@ -920,7 +920,11 @@ class YeelightColorLightSupport(YeelightBaseLight):
     @override
     def color_mode(self) -> ColorMode:
         """Return the color mode."""
-        color_mode = int(self._get_property("color_mode"))
+        raw_color_mode = self._get_property("color_mode")
+        if raw_color_mode is None:
+            # an ambilight stops reporting its mode while the main light is off
+            return ColorMode.UNKNOWN
+        color_mode = int(raw_color_mode)
         if color_mode == 1:  # RGB
             return ColorMode.RGB
         if color_mode == 2:  # color temperature
diff --git a/tests/components/yeelight/test_light.py b/tests/components/yeelight/test_light.py
index ee60c4af8efe..385afad58fa6 100644
--- a/tests/components/yeelight/test_light.py
+++ b/tests/components/yeelight/test_light.py
@@ -30,6 +30,7 @@ from homeassistant.components.homeassistant import (
 from homeassistant.components.light import (
     ATTR_BRIGHTNESS,
     ATTR_BRIGHTNESS_PCT,
+    ATTR_COLOR_MODE,
     ATTR_COLOR_TEMP_KELVIN,
     ATTR_EFFECT,
     ATTR_FLASH,
@@ -40,6 +41,7 @@ from homeassistant.components.light import (
     FLASH_SHORT,
     SERVICE_TURN_OFF,
     SERVICE_TURN_ON,
+    ColorMode,
     LightEntityFeature,
 )
 from homeassistant.components.yeelight.const import (
@@ -1333,6 +1335,58 @@ async def test_ambilight_effect(hass: HomeAssistant) -> None:
     assert ambilight_state.attributes["flowing"] is False
 
 
+async def test_ambilight_without_color_mode(
+    hass: HomeAssistant, caplog: pytest.LogCaptureFixture
+) -> None:
+    """Test the ambilight keeps updating while the bulb does not report its mode.
+
+    A ceiling light stops reporting `bg_lmode` while its main light is off.
+    """
+    assert await async_setup_component(hass, HOMEASSISTANT_DOMAIN, {})
+    mocked_bulb = _mocked_bulb()
+    capabilities = {**CAPABILITIES, "model": "ceiling10"}
+    properties = {**PROPERTIES}
+    properties.pop("bg_lmode")
+    mocked_bulb.last_properties = properties
+    mocked_bulb.bulb_type = BulbType.WhiteTempMood
+
+    config_entry = MockConfigEntry(domain=DOMAIN, data=CONFIG_ENTRY_DATA)
+    config_entry.add_to_hass(hass)
+    with (
+        _patch_discovery(capabilities=capabilities),
+        _patch_discovery_interval(),
+        patch(f"{MODULE}.AsyncBulb", return_value=mocked_bulb),
+    ):
+        assert await hass.config_entries.async_setup(config_entry.entry_id)
+        await hass.async_block_till_done()
+
+    ambilight_entity_id = "light.yeelight_ceiling10_0x15243f_ambilight"
+    state = hass.states.get(ambilight_entity_id)
+    assert state.state == STATE_ON
+    assert state.attributes[ATTR_COLOR_MODE] == ColorMode.UNKNOWN
+
+    # flash needs the mode, so it is refused instead of raising
+    await hass.services.async_call(
+        "light",
+        SERVICE_TURN_ON,
+        {ATTR_ENTITY_ID: ambilight_entity_id, ATTR_FLASH: FLASH_LONG},
+        blocking=True,
+    )
+    mocked_bulb.async_start_flow.assert_not_called()
+    assert "Flash supported currently only in RGB mode" in caplog.text
+
+    # the mode is reported again once the main light is back on
+    mocked_bulb.last_properties["bg_lmode"] = "2"
+    await hass.services.async_call(
+        HOMEASSISTANT_DOMAIN,
+        SERVICE_UPDATE_ENTITY,
+        {ATTR_ENTITY_ID: ambilight_entity_id},
+        blocking=True,
+    )
+    state = hass.states.get(ambilight_entity_id)
+    assert state.attributes[ATTR_COLOR_MODE] == ColorMode.COLOR_TEMP
+
+
 async def test_state_fails_to_update_triggers_update(hass: HomeAssistant) -> None:
     """Ensure async_get_properties is called on failed state update."""
     mocked_bulb = _mocked_bulb()