diff --git a/README.md b/README.md
index e6e0c5d..95da7de 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,16 @@ To list the available versions for the charts:
 helm search repo capi --devel --versions
 ```
 
+> **WARNING**
+>
+> The `openstack-cluster` chart depends on features in
+> [cluster-api-provider-openstack](https://github.com/kubernetes-sigs/cluster-api-provider-openstack)
+> that are merged but are not yet in a release.
+>
+> StackHPC maintain builds for cherry-picked versions of `cluster-api-provider-openstack` for use with
+> these charts. You can find these in
+> [the StackHPC fork](https://github.com/stackhpc/cluster-api-provider-openstack/releases).
+
 Currently, the following charts are available:
 
 | Chart | Description |