diff --git a/src/pyftms/client/backends/updater.py b/src/pyftms/client/backends/updater.py
index dc51867a09..a37fd5a0db 100644
--- a/src/pyftms/client/backends/updater.py
+++ b/src/pyftms/client/backends/updater.py
@@ -24,11 +24,13 @@ def __init__(
         self._serializer = get_serializer(model)
         self._prev: dict[str, Any] = {}
         self._result: dict[str, Any] = {}
+        self._seen_nonzero = False
 
     def reset(self) -> None:
         """Resetting state. Call while disconnection event."""
         self._prev.clear()
         self._result.clear()
+        self._seen_nonzero = False
 
     async def subscribe(self, cli: BleakClient, uuid: str) -> None:
         """Subscribe for notification."""
@@ -46,16 +48,23 @@ def _on_notify(self, c: BleakGATTCharacteristic, data: bytearray) -> None:
             _LOGGER.debug("'More Data' bit is set. Waiting for next data.")
             return
 
-        # My device sends a lot of null packets during wakeup and sleep mode.
-        # So I just filter null packets.
-        if any(self._result.values()):
-            update = self._result.items() ^ self._prev.items()
-
-            if update := {k: self._result[k] for k, _ in update}:
-                _LOGGER.debug("Update data: %s", update)
-                update = cast(UpdateEventData, update)  # unsafe casting
-                update = UpdateEvent(event_id="update", event_data=update)
-                self._cb(update)
-                self._prev = self._result.copy()
+        # Some devices send zero-only realtime packets during wakeup/sleep.
+        # Ignore those until we have seen a real nonzero packet, but still
+        # preserve valid nonzero-to-zero transitions after activity begins.
+        if self._result and all(value == 0 for value in self._result.values()):
+            if not self._seen_nonzero:
+                self._result.clear()
+                return
+        else:
+            self._seen_nonzero = True
+
+        update = self._result.items() ^ self._prev.items()
+
+        if update := {k: self._result[k] for k, _ in update}:
+            _LOGGER.debug("Update data: %s", update)
+            update = cast(UpdateEventData, update)  # unsafe casting
+            update = UpdateEvent(event_id="update", event_data=update)
+            self._cb(update)
+            self._prev = self._result.copy()
 
         self._result.clear()
diff --git a/tests/test_updater.py b/tests/test_updater.py
new file mode 100644
index 0000000000..828ffe98fe
--- /dev/null
+++ b/tests/test_updater.py
@@ -0,0 +1,108 @@
+from pyftms.client.backends import DataUpdater
+from pyftms.models import IndoorBikeData
+
+
+class _FakeRealtimeModel:
+    def __init__(self, data):
+        self._data = data
+
+    def _asdict(self):
+        return self._data
+
+
+class _FakeSerializer:
+    def __init__(self, *payloads):
+        self._payloads = iter(payloads)
+
+    def deserialize(self, _data):
+        return _FakeRealtimeModel(next(self._payloads))
+
+
+def test_updater_emits_zero_value_changes():
+    events = []
+    updater = DataUpdater(IndoorBikeData, events.append)
+    updater._serializer = _FakeSerializer(
+        {"speed_instant": 5.0, "cadence_instant": 50.0},
+        {"speed_instant": 0.0, "cadence_instant": 0.0},
+    )
+
+    updater._on_notify(None, bytearray(b"\x00"))
+    updater._on_notify(None, bytearray(b"\x00"))
+
+    assert len(events) == 2
+    assert events[0].event_id == "update"
+    assert events[0].event_data == {
+        "speed_instant": 5.0,
+        "cadence_instant": 50.0,
+    }
+    assert events[1].event_id == "update"
+    assert events[1].event_data == {
+        "speed_instant": 0.0,
+        "cadence_instant": 0.0,
+    }
+
+
+def test_updater_suppresses_zero_only_packets_before_first_activity():
+    events = []
+    updater = DataUpdater(IndoorBikeData, events.append)
+    updater._serializer = _FakeSerializer(
+        {"speed_instant": 0.0},
+        {"speed_instant": 0.0},
+    )
+
+    updater._on_notify(None, bytearray(b"\x00"))
+    updater._on_notify(None, bytearray(b"\x00"))
+
+    assert events == []
+
+
+def test_updater_deduplicates_repeated_zero_packets():
+    events = []
+    updater = DataUpdater(IndoorBikeData, events.append)
+    updater._serializer = _FakeSerializer(
+        {"speed_instant": 3.0},
+        {"speed_instant": 0.0},
+        {"speed_instant": 0.0},
+    )
+
+    updater._on_notify(None, bytearray(b"\x00"))
+    updater._on_notify(None, bytearray(b"\x00"))
+    updater._on_notify(None, bytearray(b"\x00"))
+
+    assert len(events) == 2
+    assert events[0].event_data == {"speed_instant": 3.0}
+    assert events[1].event_data == {"speed_instant": 0.0}
+
+
+def test_updater_emits_mixed_packets_before_seen_nonzero():
+    events = []
+    updater = DataUpdater(IndoorBikeData, events.append)
+    updater._serializer = _FakeSerializer(
+        {"speed_instant": 0.0, "cadence_instant": 50.0},
+    )
+
+    updater._on_notify(None, bytearray(b"\x00"))
+
+    assert len(events) == 1
+    assert events[0].event_data == {
+        "speed_instant": 0.0,
+        "cadence_instant": 50.0,
+    }
+
+
+def test_updater_reset_restores_startup_zero_suppression():
+    events = []
+    updater = DataUpdater(IndoorBikeData, events.append)
+    updater._serializer = _FakeSerializer(
+        {"speed_instant": 4.0},
+        {"speed_instant": 0.0},
+        {"speed_instant": 0.0},
+    )
+
+    updater._on_notify(None, bytearray(b"\x00"))
+    updater.reset()
+    updater._on_notify(None, bytearray(b"\x00"))
+    updater._on_notify(None, bytearray(b"\x00"))
+
+    assert len(events) == 1
+    assert events[0].event_data == {"speed_instant": 4.0}