diff --git a/app/Modules/Files/Http/Controllers/MyFilesController.php b/app/Modules/Files/Http/Controllers/MyFilesController.php
index 78c87b37..2c30f42d 100644
--- a/app/Modules/Files/Http/Controllers/MyFilesController.php
+++ b/app/Modules/Files/Http/Controllers/MyFilesController.php
@@ -446,6 +446,10 @@ class MyFilesController extends Controller
                 'categories' => $file->categories->pluck('id')->all(),
             ],
             'can_delete' => Gate::forUser($client)->allows('delete', $file),
+            // Their own root, where the installation gives them one. The
+            // form offers no "No folder" beside it: there is no such place
+            // for this client, and update() resolves it here anyway.
+            'home_folder_id' => $this->homeFolders->for($client)?->id,
             'can_publish' => $client->can('upload_public'),
             // The public links on this file, and where to make and revoke
             // one — the same shape the staff screen uses. A file marked
@@ -544,6 +548,15 @@ class MyFilesController extends Controller
 
         $folderId = isset($validated['folder_id']) ? (int) $validated['folder_id'] : null;
 
+        // "No folder" means the top of what this client sees, which on an
+        // installation that gives them a home folder is inside it — not the
+        // root of the library, beside the staff folders. Uploading and
+        // creating a folder already resolve it this way; the editor did
+        // not, so a client could move their own file out of their home and
+        // into the administrator's root by choosing "No folder" (reported
+        // by binghuo).
+        $folderId ??= $this->homeFolders->for($client)?->id;
+
         // The client rule, not the staff one: somewhere they could have
         // uploaded it in the first place. Same check the upload path makes,
         // so moving a file cannot reach a folder that uploading it could
diff --git a/resources/js/pages/portal/edit-file.tsx b/resources/js/pages/portal/edit-file.tsx
index 95e9209a..068d1795 100644
--- a/resources/js/pages/portal/edit-file.tsx
+++ b/resources/js/pages/portal/edit-file.tsx
@@ -51,6 +51,8 @@ interface PortalEditFileProps {
     };
     can_delete: boolean;
     can_publish: boolean;
+    /** This client's own root, where the installation gives them one. Null otherwise. */
+    home_folder_id: number | null;
     /** The public links on this file, newest first, and where to make or revoke one. */
     share_links: PortalShareLink[];
     share_link_store_url: string;
@@ -80,6 +82,7 @@ export default function PortalEditFile({
     file,
     can_delete,
     can_publish,
+    home_folder_id,
     share_links,
     share_link_store_url,
     can_set_expiration,
@@ -95,7 +98,9 @@ export default function PortalEditFile({
     const form = useForm({
         name: file.name,
         description: file.description ?? '',
-        folder_id: file.folder_id === null ? 'root' : String(file.folder_id),
+        // A file with no folder belongs in this client's own root where
+        // there is one — which is also what the server does with it.
+        folder_id: file.folder_id === null ? (home_folder_id === null ? 'root' : String(home_folder_id)) : String(file.folder_id),
         public: file.public,
         commentable: file.commentable,
         expires_at: file.expires_at ?? '',
@@ -170,7 +175,10 @@ export default function PortalEditFile({
                                     <SelectValue />
                                 </SelectTrigger>
                                 <SelectContent>
-                                    <SelectItem value="root">{t('No folder')}</SelectItem>
+                                    {/* Not offered where this client has a home
+                                        folder: "no folder" would mean the root
+                                        of the library, which is not theirs. */}
+                                    {home_folder_id === null && <SelectItem value="root">{t('No folder')}</SelectItem>}
                                     {folders.map((folder) => (
                                         <SelectItem key={folder.id} value={String(folder.id)}>
                                             <span className="flex items-center gap-1.5">
diff --git a/tests/Feature/Files/ClientHomeFoldersTest.php b/tests/Feature/Files/ClientHomeFoldersTest.php
index 3a761bdc..c80d657b 100644
--- a/tests/Feature/Files/ClientHomeFoldersTest.php
+++ b/tests/Feature/Files/ClientHomeFoldersTest.php
@@ -247,3 +247,61 @@ test('turning the setting off leaves an existing home working', function () {
     // strand them somewhere no listing looks.
     expect(app(ClientHomeFolders::class)->for($client->refresh())->id)->toBe($home->id);
 });
+
+test('a client editing their own file cannot send it to the library root', function () {
+    // Reported by binghuo: choosing "No folder" in the portal's file editor
+    // moved the file out of the client's home and into the administrator's
+    // root, beside the staff folders — the exact mess the home folder
+    // exists to end. Uploading and creating a folder already resolved an
+    // absent folder to the home; the editor did not.
+    enableHomeFolders();
+    $client = clientWhoCanUpload();
+    RolePermission::query()->create(['role_id' => $client->role_id, 'permission' => Permission::EditFiles->value]);
+    $home = app(ClientHomeFolders::class)->for($client);
+
+    $file = File::factory()->create(['uploaded_by' => $client->id, 'folder_id' => $home->id, 'name' => 'Theirs']);
+
+    $this->actingAs($client)->patch("/my-files/{$file->id}", [
+        'name' => 'Theirs',
+        'folder_id' => null,
+    ])->assertSessionHasNoErrors();
+
+    expect($file->refresh()->folder_id)->toBe($home->id);
+});
+
+test('with no home folder, no folder still means no folder', function () {
+    // The installation that never turned this on keeps what it had: a
+    // client's file sits at the root of the library because that is where
+    // every client's file sits there.
+    app(Settings::class)->set(Setting::ClientsHomeFolders, false);
+    $client = clientWhoCanUpload();
+    RolePermission::query()->create(['role_id' => $client->role_id, 'permission' => Permission::EditFiles->value]);
+    $folder = app(FolderService::class)->create('Somewhere', null);
+    shareFolderWithClient($folder, $client);
+
+    $file = File::factory()->create(['uploaded_by' => $client->id, 'folder_id' => $folder->id]);
+
+    $this->actingAs($client)->patch("/my-files/{$file->id}", [
+        'name' => 'Theirs',
+        'folder_id' => null,
+    ])->assertSessionHasNoErrors();
+
+    expect($file->refresh()->folder_id)->toBeNull();
+});
+
+test('the editor offers no "no folder" where the client has a home', function () {
+    enableHomeFolders();
+    $client = clientWhoCanUpload();
+    RolePermission::query()->create(['role_id' => $client->role_id, 'permission' => Permission::EditFiles->value]);
+    $home = app(ClientHomeFolders::class)->for($client);
+
+    $file = File::factory()->create(['uploaded_by' => $client->id, 'folder_id' => null]);
+
+    $this->actingAs($client)->get("/my-files/{$file->id}/edit")->assertInertia(
+        fn (AssertableInertia $page) => $page
+            ->component('portal/edit-file')
+            // The page hides the option and preselects this, so the form
+            // cannot post the root even by accident.
+            ->where('home_folder_id', $home->id),
+    );
+});