diff --git a/charts/thermo/templates/writer-configmap.yaml b/charts/thermo/templates/writer-configmap.yaml
index 5ddeeb6..0aafdc0 100644
--- a/charts/thermo/templates/writer-configmap.yaml
+++ b/charts/thermo/templates/writer-configmap.yaml
@@ -77,10 +77,7 @@ data:
           )
           SELECT
             event.event_id,
-            COALESCE(
-              NULLIF(measurement.value->>'updated_at', '')::timestamptz,
-              event.observed_at
-            ),
+            event.observed_at,
             event.source,
             event.collector_id,
             event.device_id,
diff --git a/charts/thermo/templates/writer-deployment.yaml b/charts/thermo/templates/writer-deployment.yaml
index 9a8c76d..ae85984 100644
--- a/charts/thermo/templates/writer-deployment.yaml
+++ b/charts/thermo/templates/writer-deployment.yaml
@@ -13,6 +13,8 @@ spec:
       {{- include "thermo.writerSelectorLabels" . | nindent 6 }}
   template:
     metadata:
+      annotations:
+        checksum/config: {{ include (print $.Template.BasePath "/writer-configmap.yaml") . | sha256sum }}
       labels:
         {{- include "thermo.writerSelectorLabels" . | nindent 8 }}
     spec: