diff --git a/README.md b/README.md
index 40f59b8..6448898 100644
--- a/README.md
+++ b/README.md
@@ -283,7 +283,7 @@ No modules.
 | <a name="input_cloudwatch_log_group_kms_key_id"></a> [cloudwatch\_log\_group\_kms\_key\_id](#input\_cloudwatch\_log\_group\_kms\_key\_id) | The ARN of the KMS Key to use when encrypting log data | `string` | `null` | no |
 | <a name="input_cloudwatch_log_group_retention_in_days"></a> [cloudwatch\_log\_group\_retention\_in\_days](#input\_cloudwatch\_log\_group\_retention\_in\_days) | The number of days to retain CloudWatch logs for the DB instance | `number` | `7` | no |
 | <a name="input_cloudwatch_log_group_skip_destroy"></a> [cloudwatch\_log\_group\_skip\_destroy](#input\_cloudwatch\_log\_group\_skip\_destroy) | Set to true if you do not wish the log group (and any logs it may contain) to be deleted at destroy time, and instead just remove the log group from the Terraform state | `bool` | `null` | no |
-| <a name="input_cluster_ca_cert_identifier"></a> [cluster\_ca\_cert\_identifier](#input\_cluster\_ca\_cert\_identifier) | The CA certificate identifier to use for the DB cluster's server certificate | `string` | `null` | no |
+| <a name="input_cluster_ca_cert_identifier"></a> [cluster\_ca\_cert\_identifier](#input\_cluster\_ca\_cert\_identifier) | The CA certificate identifier to use for the DB cluster's server certificate. Currently only supported for multi-az DB clusters | `string` | `null` | no |
 | <a name="input_cluster_members"></a> [cluster\_members](#input\_cluster\_members) | List of RDS Instances that are a part of this cluster | `list(string)` | `null` | no |
 | <a name="input_cluster_tags"></a> [cluster\_tags](#input\_cluster\_tags) | A map of tags to add to only the cluster. Used for AWS Instance Scheduler tagging | `map(string)` | `{}` | no |
 | <a name="input_cluster_timeouts"></a> [cluster\_timeouts](#input\_cluster\_timeouts) | Create, update, and delete timeout configurations for the cluster | `map(string)` | `{}` | no |
diff --git a/variables.tf b/variables.tf
index 0e952d2..3967ae0 100644
--- a/variables.tf
+++ b/variables.tf
@@ -91,7 +91,7 @@ variable "backtrack_window" {
 }
 
 variable "cluster_ca_cert_identifier" {
-  description = "The CA certificate identifier to use for the DB cluster's server certificate"
+  description = "The CA certificate identifier to use for the DB cluster's server certificate. Currently only supported for multi-az DB clusters"
   type        = string
   default     = null
 }