diff --git a/harbor/devices/camera.py b/harbor/devices/camera.py
index 821d71f..d798352 100644
--- a/harbor/devices/camera.py
+++ b/harbor/devices/camera.py
@@ -23,9 +23,10 @@
 # Known values for enumerated state fields. The device reports these in
 # mixed/upper case (e.g. "PLAYING", "GOOD"); they are normalized to the
 # lowercase values below before being stored in ``HarborDeviceState.values``.
-# A value outside these sets is still stored lowercased (and logged once),
-# so consumers that declare options up front should treat these sets as the
-# baseline, not a hard guarantee.
+# A value outside these sets is mapped to ``UNKNOWN_ENUM_VALUE`` (and logged
+# once), so a stored enum value is always a member of its set. Consumers can
+# rely on that guarantee instead of clamping the value themselves.
+UNKNOWN_ENUM_VALUE = "unknown"
 SPEAKER_STATES = frozenset({"idle", "muted", "off", "paused", "playing", "unknown"})
 STREAM_QUALITIES = frozenset({"excellent", "fair", "good", "poor", "unknown"})
 
@@ -99,21 +100,28 @@ def _normalize_enum_value(
         value: str | None,
         known_values: frozenset[str],
     ) -> str | None:
-        """Normalize an enumerated device value to a stable lowercase string."""
+        """Normalize an enumerated device value to a known lowercase member.
+
+        Returns ``None`` only when the device omitted the field. A value that
+        does not match ``known_values`` is mapped to ``UNKNOWN_ENUM_VALUE`` so
+        callers can rely on the result always being a member of the set.
+        """
         if value is None:
             return None
         normalized = value.strip().lower()
         if not normalized:
             return None
-        if normalized not in known_values and (field_name, normalized) not in self._unexpected_enum_values:
-            self._unexpected_enum_values.add((field_name, normalized))
-            _LOGGER.warning(
-                "Camera %s reported unexpected %s value %r (known values: %s)",
-                self.serial,
-                field_name,
-                normalized,
-                sorted(known_values),
-            )
+        if normalized not in known_values:
+            if (field_name, normalized) not in self._unexpected_enum_values:
+                self._unexpected_enum_values.add((field_name, normalized))
+                _LOGGER.warning(
+                    "Camera %s reported unexpected %s value %r (known values: %s)",
+                    self.serial,
+                    field_name,
+                    normalized,
+                    sorted(known_values),
+                )
+            return UNKNOWN_ENUM_VALUE
         return normalized
 
     def _apply_viewer_joined(self, viewer: ViewerInfo | None) -> None:
diff --git a/tests/test_camera_state.py b/tests/test_camera_state.py
index 0886453..713e4cd 100644
--- a/tests/test_camera_state.py
+++ b/tests/test_camera_state.py
@@ -29,7 +29,9 @@ async def test_enum_state_values_are_normalized_to_lowercase() -> None:
     assert camera.state.values["stream_quality"] in STREAM_QUALITIES
 
 
-async def test_unexpected_enum_value_is_passed_through_lowercased() -> None:
+async def test_unexpected_enum_value_maps_to_unknown() -> None:
+    """An unrecognized enum value is stored as the in-set "unknown" member."""
+
     camera = _create_camera()
 
     await camera.handle_message(
@@ -37,10 +39,29 @@ async def test_unexpected_enum_value_is_passed_through_lowercased() -> None:
         {"speaker_state": "Buffering", "stream_quality": "EXCELLENT"},
     )
 
-    assert camera.state.values["speaker_state"] == "buffering"
+    assert camera.state.values["speaker_state"] == "unknown"
+    assert camera.state.values["speaker_state"] in SPEAKER_STATES
     assert camera.state.values["stream_quality"] == "excellent"
 
 
+async def test_unexpected_enum_value_replaces_prior_valid_value() -> None:
+    """A later unrecognized value must not leave a stale valid value in place."""
+
+    camera = _create_camera()
+
+    await camera.handle_message(
+        "cameras/TEST123/events/local-livekit-heartbeat",
+        {"stream_quality": "GOOD"},
+    )
+    assert camera.state.values["stream_quality"] == "good"
+
+    await camera.handle_message(
+        "cameras/TEST123/events/local-livekit-heartbeat",
+        {"stream_quality": "DEGRADED"},
+    )
+    assert camera.state.values["stream_quality"] == "unknown"
+
+
 async def test_missing_enum_values_do_not_clear_state() -> None:
     camera = _create_camera()