diff --git a/api/v1alpha1/clusterconfig_types.go b/api/v1alpha1/clusterconfig_types.go
index 0aec5ca10..d792689d0 100644
--- a/api/v1alpha1/clusterconfig_types.go
+++ b/api/v1alpha1/clusterconfig_types.go
@@ -252,8 +252,8 @@ func (ExtraAPIServerCertSANs) VariableSchema() clusterv1.VariableSchema {
 	return clusterv1.VariableSchema{
 		OpenAPIV3Schema: clusterv1.JSONSchemaProps{
 			Description: fmt.Sprintf(
-				"Extra Subject Alternative Names for the API Server signing cert. For Docker %v are injected automatically.",
-				DefaultDockerCertSANs,
+				"Extra Subject Alternative Names for the API Server signing cert. For Docker %s are injected automatically.",
+				strings.Join(DefaultDockerCertSANs,","),
 			),
 			Type:        "array",
 			UniqueItems: true,