diff --git a/blueprints/danfoss_ally_trv_external_sensor.yaml b/blueprints/danfoss_ally_trv_external_sensor.yaml
index ba1ab38..62e792f 100644
--- a/blueprints/danfoss_ally_trv_external_sensor.yaml
+++ b/blueprints/danfoss_ally_trv_external_sensor.yaml
@@ -2,11 +2,11 @@ blueprint:
   author: runejuhl
   homeassistant:
     min_version: 2025.2.4
-  name: Radiator external temperature sensor control (0.0.3-alpha)
+  name: Radiator external temperature sensor control (0.0.4-alpha)
   description: |-
     ## Radiator external temperature sensor control
 
-    Version `0.0.3-alpha`.
+    Version `0.0.4-alpha`.
 
     Sets the `external_measured_room_sensor` value on Danfoss Ally TRV, enabling
     the TRV to adjust the valve based on an external sensor.
@@ -73,16 +73,19 @@ actions:
     # which case we pull the temperature from the sensor instead of the trigger
     # state.
     external_temperature: |-
-      {% if (trigger.id is not defined) or (trigger.to_state.state in ['unavailable', 'unknown']) %}
-      {{ states(temperature_entity) }}
+      {%- if (trigger.id is not defined) -%}
+      {%- set new_temp = states(temperature_entity) | float(-1.0) %}
       {% else %}
-      {{ trigger.to_state.state | float }}
+      {%- set new_temp = (trigger.to_state.state | float(-1.0)) -%}
       {% endif %}
+      {%- if new_temp <= 0.0 -%}
+      -8000.0
+      {%- else -%}
+      {{ new_temp * 100 | int }}
+      {%- endif -%}
+
 - action: number.set_value
   target:
     entity_id: number.{{ states[climate_entity].object_id }}_external_measured_room_sensor
   data:
-    value: |-
-      {{
-        (external_temperature * 100) | int
-      }}
+    value: "{{ external_temperature }}"