diff --git a/packages/core/platform/images/migrations/migrations/37 b/packages/core/platform/images/migrations/migrations/37
new file mode 100755
index 00000000..b8ff3147
--- /dev/null
+++ b/packages/core/platform/images/migrations/migrations/37
@@ -0,0 +1,43 @@
+#!/bin/sh
+# Migration 37 --> 38
+# Backfill spec.version on postgreses.apps.cozystack.io resources.
+#
+# Before this migration PostgreSQL had a default version field set to v18.
+# This migration sets spec.version to "v17" for any postgres app resource that
+# does not already have it set, to ensure compatibility with monitoring
+# configurations that are hardcoded to PostgreSQL 17.
+
+set -euo pipefail
+
+DEFAULT_VERSION="v17"
+
+# Skip if the CRD does not exist (postgres was never installed)
+if ! kubectl api-resources --api-group=apps.cozystack.io -o name 2>/dev/null | grep -q '^postgreses\.'; then
+  echo "CRD postgreses.apps.cozystack.io not found, skipping migration"
+  kubectl create configmap -n cozy-system cozystack-version \
+    --from-literal=version=38 --dry-run=client -o yaml | kubectl apply -f-
+  exit 0
+fi
+
+POSTGRESES=$(kubectl get postgreses.apps.cozystack.io -A -o jsonpath='{range .items[*]}{.metadata.namespace}/{.metadata.name}{"\n"}{end}')
+for resource in $POSTGRESES; do
+  NS="${resource%%/*}"
+  APP_NAME="${resource##*/}"
+
+  # Skip if spec.version is already set
+  CURRENT_VER=$(kubectl get postgreses.apps.cozystack.io -n "$NS" "$APP_NAME" \
+    -o jsonpath='{.spec.version}')
+  if [ -n "$CURRENT_VER" ]; then
+    echo "SKIP $NS/$APP_NAME: spec.version already set to '$CURRENT_VER'"
+    continue
+  fi
+
+  echo "Patching postgres/$APP_NAME in $NS: setting version=$DEFAULT_VERSION"
+
+  kubectl patch postgreses.apps.cozystack.io -n "$NS" "$APP_NAME" --type=merge \
+    --patch "{\"spec\":{\"version\":\"${DEFAULT_VERSION}\"}}"
+done
+
+# Stamp version
+kubectl create configmap -n cozy-system cozystack-version \
+  --from-literal=version=38 --dry-run=client -o yaml | kubectl apply -f-
diff --git a/packages/system/monitoring/templates/alerta/alerta-db.yaml b/packages/system/monitoring/templates/alerta/alerta-db.yaml
index fc03cd31..71df5428 100644
--- a/packages/system/monitoring/templates/alerta/alerta-db.yaml
+++ b/packages/system/monitoring/templates/alerta/alerta-db.yaml
@@ -5,6 +5,7 @@ metadata:
   name: alerta-db
 spec:
   instances: 2
+  imageName: ghcr.io/cloudnative-pg/postgresql:17.7
   {{- if .Values._cluster.scheduling }}
   {{- $rawConstraints := get .Values._cluster.scheduling "globalAppTopologySpreadConstraints" }}
   {{- if $rawConstraints }}
diff --git a/packages/system/monitoring/templates/grafana/db.yaml b/packages/system/monitoring/templates/grafana/db.yaml
index b20a8fd8..73d6502e 100644
--- a/packages/system/monitoring/templates/grafana/db.yaml
+++ b/packages/system/monitoring/templates/grafana/db.yaml
@@ -4,6 +4,7 @@ metadata:
   name: grafana-db
 spec:
   instances: 2
+  imageName: ghcr.io/cloudnative-pg/postgresql:17.7
   storage:
     size: {{ .Values.grafana.db.size }}
   {{- if .Values._cluster.scheduling }}