diff --git a/client/src/components/Admin/storage/BackendForm.test.tsx b/client/src/components/Admin/storage/BackendForm.test.tsx
index ea5df7472..1ae59f505 100644
--- a/client/src/components/Admin/storage/BackendForm.test.tsx
+++ b/client/src/components/Admin/storage/BackendForm.test.tsx
@@ -120,4 +120,15 @@ describe('BackendForm', () => {
     });
     expect(committed.options).not.toHaveProperty('region');
   });
+
+  it('FE-ADMIN-STORF-009: renaming onto another existing backend warns and blocks Apply', () => {
+    renderForm({ initial: S3_INITIAL });
+    expect(screen.getByRole('button', { name: 'Apply' })).toBeEnabled();
+    fireEvent.change(screen.getByLabelText(/Name/), { target: { value: 'uploads-local' } });
+    expect(screen.getByText(/A backend named uploads-local already exists/)).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: 'Apply' })).toBeDisabled();
+    // Keeping the original name stays allowed.
+    fireEvent.change(screen.getByLabelText(/Name/), { target: { value: 'off-box' } });
+    expect(screen.getByRole('button', { name: 'Apply' })).toBeEnabled();
+  });
 });
diff --git a/client/src/components/Admin/storage/BackendForm.tsx b/client/src/components/Admin/storage/BackendForm.tsx
index 5574c7c21..54b20e156 100644
--- a/client/src/components/Admin/storage/BackendForm.tsx
+++ b/client/src/components/Admin/storage/BackendForm.tsx
@@ -62,7 +62,7 @@ export default function BackendForm({
     if (field.kind === 'backend-ref-list') return Array.isArray(value) && value.length > 0
     return typeof value === 'string' && value.trim() !== ''
   }
-  const duplicate = initial === null && backendNames.includes(name.trim())
+  const duplicate = name.trim() !== (initial?.name ?? '') && backendNames.includes(name.trim())
   const blocked = hasPlaintextSecret({ type, options: values }) && !encryptionReady
   const canApply =
     name.trim() !== '' && !duplicate && fields.every((f) => !f.required || filled(f))
diff --git a/client/src/mobile/screens/admin/MAdminStoragePanel.tsx b/client/src/mobile/screens/admin/MAdminStoragePanel.tsx
index c8ad9a9f2..7d8c42ad5 100644
--- a/client/src/mobile/screens/admin/MAdminStoragePanel.tsx
+++ b/client/src/mobile/screens/admin/MAdminStoragePanel.tsx
@@ -68,7 +68,7 @@ function MBackendForm({
     if (field.kind === 'backend-ref-list') return Array.isArray(value) && value.length > 0
     return typeof value === 'string' && value.trim() !== ''
   }
-  const duplicate = initial === null && backendNames.includes(name.trim())
+  const duplicate = name.trim() !== (initial?.name ?? '') && backendNames.includes(name.trim())
   const blocked = hasPlaintextSecret({ type, options: values }) && !encryptionReady
   const canApply = name.trim() !== '' && !duplicate && fields.every((f) => !f.required || filled(f))
 
diff --git a/client/tests/unit/mobile/admin/MAdminStoragePanel.test.tsx b/client/tests/unit/mobile/admin/MAdminStoragePanel.test.tsx
index ee354f3dd..11c3f789e 100644
--- a/client/tests/unit/mobile/admin/MAdminStoragePanel.test.tsx
+++ b/client/tests/unit/mobile/admin/MAdminStoragePanel.test.tsx
@@ -90,4 +90,13 @@ describe('MAdminStoragePanel', () => {
     fireEvent.click(screen.getByRole('button', { name: 'Save changes' }));
     expect(await screen.findByText('registry says no')).toBeInTheDocument();
   });
+
+  it('FE-MOB-MSTOR-005: renaming onto another existing backend warns and blocks Apply', async () => {
+    await renderPanel();
+    fireEvent.click(within(screen.getByTestId('m-storage-backend-off-box')).getByRole('button', { name: 'Edit' }));
+    const nameInput = screen.getByDisplayValue('off-box');
+    fireEvent.change(nameInput, { target: { value: 'uploads-local' } });
+    expect(screen.getByText(/A backend named uploads-local already exists/)).toBeInTheDocument();
+    expect(screen.getByRole('button', { name: 'Apply' })).toBeDisabled();
+  });
 });