diff --git a/variables.tf b/variables.tf
index 290be76..1f59ea3 100644
--- a/variables.tf
+++ b/variables.tf
@@ -33,10 +33,12 @@ variable "db_allocated_storage" {
       : var.storage_type == "gp3" ? var.allocated_storage >= 20
       : true
     )
-    error_message = "Invalid 'allocated_storage':
+    error_message = <<EOF
+    "Invalid 'allocated_storage':
       - When 'storage_type' is 'io2' and 'engine' is SQL Server, it must be at least 20 GiB.
       - When 'storage_type' is 'io2' and 'engine' is not SQL Server, it must be at least 100 GiB.
       - When 'storage_type' is 'gp3', it must be at least 20 GiB."
+    EOF
   }
 }