diff --git a/digitalocean/kubernetes/resource_kubernetes_cluster.go b/digitalocean/kubernetes/resource_kubernetes_cluster.go
index 9abb46df8..7167168e3 100644
--- a/digitalocean/kubernetes/resource_kubernetes_cluster.go
+++ b/digitalocean/kubernetes/resource_kubernetes_cluster.go
@@ -121,9 +121,10 @@ func ResourceDigitalOceanKubernetesCluster() *schema.Resource {
 				Elem: &schema.Resource{
 					Schema: map[string]*schema.Schema{
 						"day": {
-							Type:     schema.TypeString,
-							Optional: true,
-							Computed: true,
+							Type:         schema.TypeString,
+							Optional:     true,
+							Computed:     true,
+							ValidateFunc: validation.IsDayOfTheWeek(true),
 						},
 						"start_time": {
 							Type:     schema.TypeString,