diff --git a/l10n/messages.pot b/l10n/messages.pot
index d4f84560c..ad6eded33 100644
--- a/l10n/messages.pot
+++ b/l10n/messages.pot
@@ -2,12 +2,21 @@ msgid ""
 msgstr ""
 "Content-Type: text/plain; charset=UTF-8\n"
 
+msgid "\"{char}\" is not allowed inside a name."
+msgstr ""
+
+msgid "\"{extension}\" is not an allowed name."
+msgstr ""
+
 msgid "\"{name}\" is an invalid folder name."
 msgstr ""
 
 msgid "\"{name}\" is not an allowed folder name"
 msgstr ""
 
+msgid "\"{segment}\" is a reserved name and not allowed."
+msgstr ""
+
 msgid "\"/\" is not allowed inside a folder name."
 msgstr ""
 
@@ -76,6 +85,9 @@ msgstr ""
 msgid "Home"
 msgstr ""
 
+msgid "Invalid name."
+msgstr ""
+
 msgid "Modified"
 msgstr ""
 
@@ -88,6 +100,15 @@ msgstr ""
 msgid "Name"
 msgstr ""
 
+msgid "Names must not be empty."
+msgstr ""
+
+msgid "Names must not end with \"{extension}\"."
+msgstr ""
+
+msgid "Names must not start with a dot."
+msgstr ""
+
 msgid "New"
 msgstr ""
 
diff --git a/lib/components/PublicAuthPrompt.vue b/lib/components/PublicAuthPrompt.vue
index bd5a10ffc..d772755c9 100644
--- a/lib/components/PublicAuthPrompt.vue
+++ b/lib/components/PublicAuthPrompt.vue
@@ -6,11 +6,12 @@
 <script setup lang="ts">
 import { setGuestNickname } from '@nextcloud/auth'
 import { getBuilder } from '@nextcloud/browser-storage'
-import { showError } from '@nextcloud/dialogs'
 import { computed, ref, useTemplateRef, watch } from 'vue'
 import NcDialog from '@nextcloud/vue/components/NcDialog'
 import NcNoteCard from '@nextcloud/vue/components/NcNoteCard'
 import NcTextField from '@nextcloud/vue/components/NcTextField'
+import { showError } from '../toast.ts'
+import { getGuestNameValidity } from '../utils/guestNameValidity.ts'
 import { t } from '../utils/l10n.ts'
 import { logger } from '../utils/logger.ts'
 
@@ -70,6 +71,18 @@ watch(() => props.nickname, () => {
 	name.value = props.nickname
 })
 
+watch(name, (newName) => {
+	// Check validity of the new name
+	const validity = getGuestNameValidity(newName)
+	if (!validity) {
+		// If the nickname is not valid, show an error
+		inputElement.value.setCustomValidity(validity)
+		inputElement.value.reportValidity()
+		inputElement.value.focus()
+		return
+	}
+})
+
 const buttons = computed(() => {
 	const cancelButton = {
 		label: t('Cancel'),
@@ -97,6 +110,15 @@ const buttons = computed(() => {
 function onSubmit() {
 	const nickname = name.value.trim()
 
+	const validity = getGuestNameValidity(nickname)
+	if (validity) {
+		// If the nickname is not valid, show an error
+		inputElement.value.setCustomValidity(validity)
+		inputElement.value.reportValidity()
+		inputElement.value.focus()
+		return
+	}
+
 	if (nickname === '') {
 		// Show error if the nickname is empty
 		inputElement.value.setCustomValidity(t('You cannot leave the name empty.'))
diff --git a/lib/public-auth.ts b/lib/public-auth.ts
index 69348f917..8c66483c1 100644
--- a/lib/public-auth.ts
+++ b/lib/public-auth.ts
@@ -23,6 +23,5 @@ export async function showGuestUserPrompt(props: GuestUserPromptOptions): Promis
 		defineAsyncComponent(() => import('./components/PublicAuthPrompt.vue')),
 		props,
 	)
-	/// @ts-expect-error TODO: remove when fixed upstream: https://github.com/nextcloud-libraries/nextcloud-vue/issues/6902
 	return name
 }
diff --git a/lib/utils/guestNameValidity.ts b/lib/utils/guestNameValidity.ts
new file mode 100644
index 000000000..28ff160ae
--- /dev/null
+++ b/lib/utils/guestNameValidity.ts
@@ -0,0 +1,45 @@
+/*!
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+import { InvalidFilenameError, InvalidFilenameErrorReason, validateFilename } from '@nextcloud/files'
+import { t } from '../utils/l10n.ts'
+
+/**
+ * Get the validity of a filename (empty if valid).
+ * This can be used for `setCustomValidity` on input elements
+ *
+ * @param name The filename
+ */
+export function getGuestNameValidity(name: string): string {
+	if (name.trim() === '') {
+		return t('Names must not be empty.')
+	}
+
+	if (name.startsWith('.')) {
+		return t('Names must not start with a dot.')
+	}
+
+	try {
+		validateFilename(name)
+		return ''
+	} catch (error) {
+		if (!(error instanceof InvalidFilenameError)) {
+			throw error
+		}
+
+		switch (error.reason) {
+			case InvalidFilenameErrorReason.Character:
+				return t('"{char}" is not allowed inside a name.', { char: error.segment })
+			case InvalidFilenameErrorReason.ReservedName:
+				return t('"{segment}" is a reserved name and not allowed.', { segment: error.segment })
+			case InvalidFilenameErrorReason.Extension:
+				if (error.segment.match(/\.[a-z]/i)) {
+					return t('"{extension}" is not an allowed name.', { extension: error.segment })
+				}
+				return t('Names must not end with "{extension}".', { extension: error.segment })
+			default:
+				return t('Invalid name.')
+		}
+	}
+}