diff --git a/main.tf b/main.tf
index cf0b6d9..86b2e1a 100644
--- a/main.tf
+++ b/main.tf
@@ -151,5 +151,8 @@ resource "aws_instance" "ubuntu_instance" {
     delete_on_termination = true
   }
 
-  user_data = var.user_data
+  # Use templatefile for user_data: https://developer.hashicorp.com/terraform/language/v1.2.x/functions/templatefile
+  user_data                   = templatefile("${path.module}/user_data.sh", {
+    extra_key = var.SSH_PUBLIC_KEY
+  })
 }