diff --git a/builtin/providers/aws/resource_aws_db_instance.go b/builtin/providers/aws/resource_aws_db_instance.go
index 47a98b73d..6ca1916b5 100644
--- a/builtin/providers/aws/resource_aws_db_instance.go
+++ b/builtin/providers/aws/resource_aws_db_instance.go
@@ -46,6 +46,10 @@ func resourceAwsDbInstance() *schema.Resource {
 				Type:     schema.TypeString,
 				Required: true,
 				ForceNew: true,
+				StateFunc: func(v interface{}) string {
+					value := v.(string)
+					return strings.ToLower(value)
+				},
 			},
 
 			"engine_version": &schema.Schema{