diff --git a/src/amcrest2mqtt/interface.py b/src/amcrest2mqtt/interface.py
index 9552ef6..93e1f35 100644
--- a/src/amcrest2mqtt/interface.py
+++ b/src/amcrest2mqtt/interface.py
@@ -104,7 +104,7 @@ class AmcrestServiceProtocol(Protocol):
     def mqtt_on_message(self, client: Client, userdata: Any, msg: MQTTMessage) -> None: ...
     def mqtt_on_subscribe(self, client: Client, userdata: Any, mid: int, reason_code_list: list[ReasonCode], properties: Properties) -> None: ...
     def mqtt_on_log(self, client: Client, userdata: Any, paho_log_level: int, msg: str) -> None: ...
-    def mqtt_safe_publish(self, topic: str, payload: str | bool | int | dict, **kwargs: Any) -> None: ...
+    def mqtt_safe_publish(self, topic: str, payload: str | bool | int | dict | None, **kwargs: Any) -> None: ...
     def mqttc_create(self) -> None: ...
     def publish_device_availability(self, device_id: str, online: bool = True) -> None: ...
     def publish_device_discovery(self, device_id: str) -> None: ...
diff --git a/src/amcrest2mqtt/mixins/amcrest.py b/src/amcrest2mqtt/mixins/amcrest.py
index a74d754..d6fea1a 100644
--- a/src/amcrest2mqtt/mixins/amcrest.py
+++ b/src/amcrest2mqtt/mixins/amcrest.py
@@ -143,7 +143,7 @@ class AmcrestMixin:
             "component_type": "sensor",
             "name": "Recording url",
             "uniq_id": self.mqtt_helper.dev_unique_id(device_id, "recording_url"),
-            "stat_t": self.mqtt_helper.stat_t(device_id, "recording_url"),
+            "stat_t": self.mqtt_helper.stat_t(device_id, "sensor", "recording_url"),
             "avty_t": self.mqtt_helper.avty_t(device_id),
             "clip_url": f"media-source://media_source/local/Videos/amcrest/{device["device_name"]}-latest.mp4",
             "icon": "mdi:web",
@@ -343,8 +343,8 @@ class AmcrestMixin:
             sensor={
                 "motion_region": "n/a",
                 "event_text": "",
-                "event_time": "unknown",
-                "recording_time": "unknown",
+                "event_time": None,
+                "recording_time": None,
                 "recording_url": "",
             },
         )
diff --git a/src/amcrest2mqtt/mixins/mqtt.py b/src/amcrest2mqtt/mixins/mqtt.py
index 6f738e8..3022603 100644
--- a/src/amcrest2mqtt/mixins/mqtt.py
+++ b/src/amcrest2mqtt/mixins/mqtt.py
@@ -203,7 +203,7 @@ class MqttMixin:
         joined = "; ".join(reason_names) if reason_names else "none"
         self.logger.debug(f"MQTT subscribed (mid={mid}): {joined}")
 
-    def mqtt_safe_publish(self: Amcrest2Mqtt, topic: str, payload: str | bool | int | dict, **kwargs: Any) -> None:
+    def mqtt_safe_publish(self: Amcrest2Mqtt, topic: str, payload: str | bool | int | dict | None, **kwargs: Any) -> None:
         if not topic:
             raise ValueError("Cannot post to a blank topic")
         if isinstance(payload, dict) and ("component" in payload or "//////" in payload):
@@ -212,6 +212,9 @@ class MqttMixin:
             self.logger.warning(f"payload: {payload}")
             raise ValueError("Possible invalid payload. topic: {topic} payload: {payload}")
         try:
-            self.mqttc.publish(topic, cast(PayloadType, payload), **kwargs)
+            if payload is None:
+                self.mqttc.publish(topic, "null", **kwargs)
+            else:
+                self.mqttc.publish(topic, cast(PayloadType, payload), **kwargs)
         except Exception as e:
             self.logger.warning(f"MQTT publish failed for {topic} with {payload[:120] if isinstance(payload, str) else payload}: {e}")