diff --git a/builtin/providers/digitalocean/resource_digitalocean_droplet.go b/builtin/providers/digitalocean/resource_digitalocean_droplet.go
index 88c0c6d07..c14b248c6 100644
--- a/builtin/providers/digitalocean/resource_digitalocean_droplet.go
+++ b/builtin/providers/digitalocean/resource_digitalocean_droplet.go
@@ -39,6 +39,10 @@ func resourceDigitalOceanDroplet() *schema.Resource {
 			"size": &schema.Schema{
 				Type:     schema.TypeString,
 				Required: true,
+				StateFunc: func(val interface{}) string {
+					// DO API V2 size slug is always lowercase
+					return strings.ToLower(val.(string))
+				},
 			},
 
 			"status": &schema.Schema{