diff --git a/CHANGELOG.md b/CHANGELOG.md
index f8adaba..647b662 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 - Fixed dialog panels growing beyond the viewport; dialog content is now constrained and scrollable (via [#556](https://github.com/tale/headplane/pull/556)).
 - Fixed focus rings on inputs and buttons inside dialogs being clipped by the scrollable content container.
 - Fixed tooltips on the last row of the machines table being clipped by the viewport; tooltips now anchor above the trigger with collision padding (closes [#508](https://github.com/tale/headplane/issues/508)).
+- Fixed the "Register Machine Key" dialog passing the Headscale numeric user id instead of the username. Headscale's `RegisterNodeRequest.user` proto field is a `string` that is looked up via `GetUserByName` (no numeric fallback), so registration was failing whenever the selected owner's display name differed from their numeric id (closes [#532](https://github.com/tale/headplane/issues/532)).
 - Corrected the Docker healthcheck example in the docs to use the required `CMD` prefix so reverse proxies don't see the container as unhealthy (closes [#535](https://github.com/tale/headplane/issues/535)).
 
 ---
diff --git a/app/routes/machines/dialogs/new.tsx b/app/routes/machines/dialogs/new.tsx
index 2bbefcb..523b723 100644
--- a/app/routes/machines/dialogs/new.tsx
+++ b/app/routes/machines/dialogs/new.tsx
@@ -52,7 +52,9 @@ export default function NewMachine(data: NewMachineProps) {
             onValueChange={(v) => form.setValue("user", v)}
             placeholder="Select a user"
             items={data.users.map((user) => ({
-              value: user.id,
+              // Headscale's v1/node/register endpoint resolves the owner by
+              // username via GetUserByName, so we must pass user.name (not id).
+              value: user.name,
               label: getUserDisplayName(user),
             }))}
           />