diff --git a/README.md b/README.md
index 225c95b8..3e81bece 100644
--- a/README.md
+++ b/README.md
@@ -766,6 +766,16 @@ sudo cp nginx.conf /etc/nginx/sites-available/dental-app
 sudo nginx -t && sudo systemctl reload nginx
 ```
 
+> **If `nginx -t` fails with `could not build server_names_hash, you should increase
+> server_names_hash_bucket_size: 64`:** the `local-<office>.mydentalofficemanagement.com`
+> hostname is too long for nginx's default hash bucket size. Fix it in the main config (not this
+> repo's `nginx.conf`) — `/etc/nginx/nginx.conf` already has a commented-out line for this inside
+> the `http { }` block:
+> ```sh
+> sudo sed -i 's/# server_names_hash_bucket_size 64;/server_names_hash_bucket_size 128;/' /etc/nginx/nginx.conf
+> sudo nginx -t && sudo systemctl reload nginx
+> ```
+
 ### Step 7 — Allow the new hostname in Vite and backend CORS
 
 - `apps/Frontend/vite.config.ts` → add the hostname to `server.allowedHosts`