diff --git a/api/v1alpha1/clusterextension_types.go b/api/v1alpha1/clusterextension_types.go
index 907e762d1..e18ff68a4 100644
--- a/api/v1alpha1/clusterextension_types.go
+++ b/api/v1alpha1/clusterextension_types.go
@@ -73,6 +73,7 @@ type ClusterExtensionSpec struct {
 
 	//+kubebuilder:validation:Pattern:=^[a-z0-9]([-a-z0-9]*[a-z0-9])?$
 	//+kubebuilder:validation:MaxLength:=63
+	//+kubebuilder:validation:XValidation:rule="self == oldSelf",message="installNamespace is immutable"
 	//
 	// installNamespace is the namespace where the bundle should be installed. However, note that
 	// the bundle may contain resources that are cluster-scoped or that are
diff --git a/config/base/crd/bases/olm.operatorframework.io_clusterextensions.yaml b/config/base/crd/bases/olm.operatorframework.io_clusterextensions.yaml
index 9c41127f5..f1da4ae8a 100644
--- a/config/base/crd/bases/olm.operatorframework.io_clusterextensions.yaml
+++ b/config/base/crd/bases/olm.operatorframework.io_clusterextensions.yaml
@@ -52,6 +52,9 @@ spec:
                 maxLength: 63
                 pattern: ^[a-z0-9]([-a-z0-9]*[a-z0-9])?$
                 type: string
+                x-kubernetes-validations:
+                - message: installNamespace is immutable
+                  rule: self == oldSelf
               packageName:
                 maxLength: 48
                 pattern: ^[a-z0-9]+(-[a-z0-9]+)*$