diff --git a/app/soapbox/features/notifications/components/notification.tsx b/app/soapbox/features/notifications/components/notification.tsx
index b413517e6c..a6e7e9514e 100644
--- a/app/soapbox/features/notifications/components/notification.tsx
+++ b/app/soapbox/features/notifications/components/notification.tsx
@@ -9,9 +9,9 @@ import { HStack, Text, Emoji } from 'soapbox/components/ui';
 import AccountContainer from 'soapbox/containers/account_container';
 import StatusContainer from 'soapbox/containers/status_container';
 import { useAppSelector } from 'soapbox/hooks';
+import { NotificationType, validType } from 'soapbox/utils/notification';
 
 import type { ScrollPosition } from 'soapbox/components/status';
-import type { NotificationType } from 'soapbox/normalizers/notification';
 import type { Account, Status, Notification as NotificationEntity } from 'soapbox/types/entities';
 
 const notificationForScreenReader = (intl: IntlShape, message: string, timestamp: Date) => {
@@ -48,7 +48,7 @@ const icons: Record<NotificationType, string> = {
   user_approved: require('@tabler/icons/icons/user-plus.svg'),
 };
 
-const messages: Record<string | number | symbol, MessageDescriptor> = defineMessages({
+const messages: Record<NotificationType, MessageDescriptor> = defineMessages({
   follow: {
     id: 'notification.follow',
     defaultMessage: '{name} followed you',
@@ -221,7 +221,7 @@ const Notification: React.FC<INotificaton> = (props) => {
           className='w-4 h-4 flex-none'
         />
       );
-    } else if (type) {
+    } else if (validType(type)) {
       return (
         <Icon
           src={icons[type]}
@@ -279,9 +279,9 @@ const Notification: React.FC<INotificaton> = (props) => {
 
   const targetName = notification.target && typeof notification.target === 'object' ? notification.target.acct : '';
 
-  const message: React.ReactNode = type && account && typeof account === 'object' ? buildMessage(intl, type, account, notification.total_count, targetName, instance.title) : null;
+  const message: React.ReactNode = validType(type) && account && typeof account === 'object' ? buildMessage(intl, type, account, notification.total_count, targetName, instance.title) : null;
 
-  const ariaLabel = messages[type] ? (
+  const ariaLabel = validType(type) ? (
     notificationForScreenReader(
       intl,
       intl.formatMessage(messages[type], {
diff --git a/app/soapbox/normalizers/notification.ts b/app/soapbox/normalizers/notification.ts
index 2bac3f2b3e..9b34278b6e 100644
--- a/app/soapbox/normalizers/notification.ts
+++ b/app/soapbox/normalizers/notification.ts
@@ -11,19 +11,6 @@ import {
 
 import type { Account, Status, EmbeddedEntity } from 'soapbox/types/entities';
 
-export type NotificationType =
-  'follow'
-  | 'follow_request'
-  | 'mention'
-  | 'reblog'
-  | 'favourite'
-  | 'poll'
-  | 'status'
-  | 'move'
-  | 'pleroma:chat_mention'
-  | 'pleroma:emoji_reaction'
-  | 'user_approved';
-
 // https://docs.joinmastodon.org/entities/notification/
 export const NotificationRecord = ImmutableRecord({
   account: null as EmbeddedEntity<Account>,
@@ -33,7 +20,7 @@ export const NotificationRecord = ImmutableRecord({
   id: '',
   status: null as EmbeddedEntity<Status>,
   target: null as EmbeddedEntity<Account>, // move
-  type: '' as NotificationType | '',
+  type: '',
   total_count: null as number | null, // grouped notifications
 });
 
diff --git a/app/soapbox/utils/notification.ts b/app/soapbox/utils/notification.ts
new file mode 100644
index 0000000000..635d16f293
--- /dev/null
+++ b/app/soapbox/utils/notification.ts
@@ -0,0 +1,25 @@
+/** Notification types known to Soapbox. */
+const NOTIFICATION_TYPES = [
+  'follow',
+  'follow_request',
+  'mention',
+  'reblog',
+  'favourite',
+  'poll',
+  'status',
+  'move',
+  'pleroma:chat_mention',
+  'pleroma:emoji_reaction',
+  'user_approved',
+] as const;
+
+type NotificationType = typeof NOTIFICATION_TYPES[number];
+
+/** Ensure the Notification is a valid, known type. */
+const validType = (type: string): type is NotificationType => NOTIFICATION_TYPES.includes(type as any);
+
+export {
+  NOTIFICATION_TYPES,
+  NotificationType,
+  validType,
+};