diff --git a/modules/runner-binaries-syncer/variables.tf b/modules/runner-binaries-syncer/variables.tf
index d2daafec3f..1997c4b7e4 100644
--- a/modules/runner-binaries-syncer/variables.tf
+++ b/modules/runner-binaries-syncer/variables.tf
@@ -17,6 +17,12 @@ variable "environment" {
 variable "distribution_bucket_name" {
   description = "Bucket for storing the action runner distribution."
   type        = string
+  
+  # Make sure the bucket name only contains legal characters
+  validation {
+    error_message = "Only lowercase alphanumeric characters and hyphens allowed in the bucket name."
+    condition = can(regex("^[a-z0-9-]*$", var.distribution_bucket_name))
+  }
 }
 
 variable "lambda_schedule_expression" {