diff --git a/CHANGELOG.md b/CHANGELOG.md
index e957710fdb45f6f2e6ef4832b688209951e5c5fa..51208e3b874c4f21963513e62d2ed2edc0ecddc7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,7 +5,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-* Nothing yet!
+* Update:
+  * Kube-prometheus-stack to helm chart version 18.0.12
 
 ## [0.7.0] - 2021-08-19
 
diff --git a/flux2/apps/monitoring/kube-prometheus-stack-release.yaml b/flux2/apps/monitoring/kube-prometheus-stack-release.yaml
index 259bc5cc6d913d7874e9173b7e6f703878106c98..6a6bbe2ebdb31b121a77b1509887d5c5f091546b 100644
--- a/flux2/apps/monitoring/kube-prometheus-stack-release.yaml
+++ b/flux2/apps/monitoring/kube-prometheus-stack-release.yaml
@@ -9,7 +9,7 @@ spec:
   chart:
     spec:
       chart: kube-prometheus-stack
-      version: 16.12.0
+      version: 18.0.12
       sourceRef:
         kind: HelmRepository
         name: prometheus-community
@@ -17,6 +17,10 @@ spec:
   interval: 1h
   install:
     timeout: 10m
+  upgrade:
+    # Replace (update) CRDs upon upgrade. This is necessary to upgrade from
+    # kube-prometheus-stack 16.x to 18.x
+    crds: CreateReplace
   valuesFrom:
     - kind: ConfigMap
       name: oas-kube-prometheus-stack-values
@@ -28,3 +32,4 @@ spec:
     - kind: Secret
       name: oas-kube-prometheus-stack-override
       optional: true
+