diff --git a/apps/dav/src/service/CalendarService.spec.ts b/apps/dav/src/service/CalendarService.spec.ts
new file mode 100644
index 0000000000000..f41f362771989
--- /dev/null
+++ b/apps/dav/src/service/CalendarService.spec.ts
@@ -0,0 +1,48 @@
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { getEmptySlots, saveScheduleInboxAvailability } from './CalendarService.ts'
+
+const customRequest = vi.fn()
+vi.mock('../dav/client.ts', () => ({
+	getClient: () => ({ customRequest }),
+}))
+
+afterEach(() => {
+	customRequest.mockReset()
+})
+
+describe('saveScheduleInboxAvailability', () => {
+	it('removes the availability property when there are no slots', async () => {
+		await saveScheduleInboxAvailability(getEmptySlots(), 'UTC')
+
+		expect(customRequest).toHaveBeenCalledOnce()
+		const [path, { method, data }] = customRequest.mock.calls[0]
+		expect(path).toBe('inbox')
+		expect(method).toBe('PROPPATCH')
+		expect(data).toContain('<x0:remove>')
+		expect(data).not.toContain('<x0:set>')
+		expect(data).not.toContain('VAVAILABILITY')
+	})
+
+	it('sets the availability property when there are slots', async () => {
+		const slots = getEmptySlots()
+		slots.MO = [{
+			start: new Date('2026-10-12T09:00:00Z').getTime() / 1000,
+			end: new Date('2026-10-12T17:00:00Z').getTime() / 1000,
+		}]
+
+		await saveScheduleInboxAvailability(slots, 'UTC')
+
+		expect(customRequest).toHaveBeenCalledOnce()
+		const [path, { method, data }] = customRequest.mock.calls[0]
+		expect(path).toBe('inbox')
+		expect(method).toBe('PROPPATCH')
+		expect(data).toContain('<x0:set>')
+		expect(data).toContain('BEGIN:VAVAILABILITY')
+		expect(data).toContain('BEGIN:AVAILABLE')
+	})
+})
diff --git a/apps/dav/src/service/CalendarService.ts b/apps/dav/src/service/CalendarService.ts
index 2a60e87f44cec..17613d233430c 100644
--- a/apps/dav/src/service/CalendarService.ts
+++ b/apps/dav/src/service/CalendarService.ts
@@ -66,6 +66,24 @@ export async function saveScheduleInboxAvailability(slots, timezoneId) {
 		day: dayId,
 	})))]
 
+	// An empty VAVAILABILITY means unavailable at all times (RFC 7953), so remove the property instead
+	if (all.length === 0) {
+		logger.debug('No availability slots, removing availability')
+
+		await getClient().customRequest('inbox', {
+			method: 'PROPPATCH',
+			data: `<?xml version="1.0"?>
+			<x0:propertyupdate xmlns:x0="DAV:">
+			  <x0:remove>
+				<x0:prop>
+				  <x1:calendar-availability xmlns:x1="urn:ietf:params:xml:ns:caldav"/>
+				</x0:prop>
+			  </x0:remove>
+			</x0:propertyupdate>`,
+		})
+		return
+	}
+
 	const vavailability = slotsToVavailability(all, timezoneId)
 
 	logger.debug('New availability ical created', {