diff --git a/acmpca/certificate.tf b/acmpca/certificate.tf
index c9baf22..f988749 100644
--- a/acmpca/certificate.tf
+++ b/acmpca/certificate.tf
@@ -8,7 +8,7 @@ locals {
 
   output_file_directory  = var.output_file_directory != null ? var.output_file_directory : format("%v/%v", path.root, "certs")
   _cert_filename         = coalesce(var.certificate_cn, local.cert_dns)
-  generate_cert_filename = try(regex("[^a-zA-Z0-9_-.]", local._cert_filename), false)
+  generate_cert_filename = try(regex("[^a-zA-Z0-9_\\.-]", local._cert_filename), "") != ""
   cert_filename          = local.generate_cert_filename ? random_uuid.filename[0].result : local._cert_filename
 }