diff --git a/modules/cloudsql-instance/variables.tf b/modules/cloudsql-instance/variables.tf
index 86d05e244..af7a757cb 100644
--- a/modules/cloudsql-instance/variables.tf
+++ b/modules/cloudsql-instance/variables.tf
@@ -41,7 +41,7 @@ variable "backup_configuration" {
     log_retention_days             = optional(number, 7)
     point_in_time_recovery_enabled = optional(bool)
     retention_count                = optional(number, 7)
-    retain_backups_on_delete       = optional(bool, false)
+    retain_backups_on_delete       = optional(bool)
     final_backup = optional(object({
       enabled        = optional(bool, false)
       retention_days = optional(number, 7)
@@ -55,7 +55,7 @@ variable "backup_configuration" {
     log_retention_days             = 7
     point_in_time_recovery_enabled = null
     retention_count                = 7
-    retain_backups_on_delete       = false
+    retain_backups_on_delete       = null
     final_backup                   = null
   }
 }