diff --git a/ts/model-types.d.ts b/ts/model-types.d.ts
index cf944ea4b7..f45629bb94 100644
--- a/ts/model-types.d.ts
+++ b/ts/model-types.d.ts
@@ -71,6 +71,13 @@ export type RetryOptions = Readonly<{
   now: number;
 }>;
 
+export type GroupV1Update = {
+  avatarUpdated?: boolean;
+  joined?: Array<string>;
+  left?: string | 'You';
+  name?: string;
+};
+
 export type MessageAttributesType = {
   bodyPending?: boolean;
   bodyRanges?: BodyRangesType;
@@ -86,12 +93,7 @@ export type MessageAttributesType = {
   expirationStartTimestamp?: number | null;
   expireTimer?: number;
   groupMigration?: GroupMigrationType;
-  group_update?: {
-    avatarUpdated: boolean;
-    joined: Array<string>;
-    left: string | 'You';
-    name: string;
-  };
+  group_update?: GroupV1Update;
   hasAttachments?: boolean;
   hasFileAttachments?: boolean;
   hasVisualMediaAttachments?: boolean;
diff --git a/ts/models/messages.ts b/ts/models/messages.ts
index 75197236c3..35b01312a2 100644
--- a/ts/models/messages.ts
+++ b/ts/models/messages.ts
@@ -1,8 +1,10 @@
 // Copyright 2020-2021 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
+import { isEmpty } from 'lodash';
 import {
   CustomError,
+  GroupV1Update,
   MessageAttributesType,
   RetryOptions,
   ReactionAttributesType,
@@ -10,7 +12,8 @@ import {
   QuotedMessageType,
   WhatIsThis,
 } from '../model-types.d';
-import { find } from '../util/iterables';
+import { map, filter, find } from '../util/iterables';
+import { isNotNil } from '../util/isNotNil';
 import { DataMessageClass } from '../textsecure.d';
 import { ConversationModel } from './conversations';
 import { MessageStatusType } from '../components/conversation/Message';
@@ -2687,7 +2690,8 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
 
           // GroupV1
           if (!hasGroupV2Prop && dataMessage.group) {
-            const pendingGroupUpdate = [];
+            const pendingGroupUpdate: GroupV1Update = {};
+
             const memberConversations: Array<ConversationModel> = await Promise.all(
               dataMessage.group.membersE164.map((e164: string) =>
                 window.ConversationController.getOrCreateAndWait(
@@ -2710,7 +2714,7 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
               };
 
               if (dataMessage.group.name !== conversation.get('name')) {
-                pendingGroupUpdate.push(['name', dataMessage.group.name]);
+                pendingGroupUpdate.name = dataMessage.group.name;
               }
 
               const avatarAttachment = dataMessage.group.avatar;
@@ -2773,7 +2777,7 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
 
                 attributes.avatar = avatar;
 
-                pendingGroupUpdate.push(['avatarUpdated', true]);
+                pendingGroupUpdate.avatarUpdated = true;
               } else {
                 window.log.info(
                   'handleDataMessage: Group avatar hash matched; not replacing group avatar'
@@ -2787,11 +2791,11 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
               );
               if (difference.length > 0) {
                 // Because GroupV1 groups are based on e164 only
-                const e164s = difference.map(id => {
-                  const c = window.ConversationController.get(id);
-                  return c ? c.get('e164') : null;
-                });
-                pendingGroupUpdate.push(['joined', e164s]);
+                const maybeE164s = map(difference, id =>
+                  window.ConversationController.get(id)?.get('e164')
+                );
+                const e164s = filter(maybeE164s, isNotNil);
+                pendingGroupUpdate.joined = [...e164s];
               }
               if (conversation.get('left')) {
                 window.log.warn('re-added to a left group');
@@ -2815,9 +2819,9 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
 
               if (isMe(sender.attributes)) {
                 attributes.left = true;
-                pendingGroupUpdate.push(['left', 'You']);
+                pendingGroupUpdate.left = 'You';
               } else {
-                pendingGroupUpdate.push(['left', sender.get('id')]);
+                pendingGroupUpdate.left = sender.get('id');
               }
               attributes.members = _.without(
                 conversation.get('members'),
@@ -2825,15 +2829,8 @@ export class MessageModel extends window.Backbone.Model<MessageAttributesType> {
               );
             }
 
-            if (pendingGroupUpdate.length) {
-              const groupUpdate = pendingGroupUpdate.reduce(
-                (acc, [key, value]) => {
-                  acc[key] = value;
-                  return acc;
-                },
-                {} as typeof window.WhatIsThis
-              );
-              message.set({ group_update: groupUpdate });
+            if (!isEmpty(pendingGroupUpdate)) {
+              message.set('group_update', pendingGroupUpdate);
             }
           }
 
diff --git a/ts/state/selectors/message.ts b/ts/state/selectors/message.ts
index f8805b3ab2..7001d90d8d 100644
--- a/ts/state/selectors/message.ts
+++ b/ts/state/selectors/message.ts
@@ -671,7 +671,7 @@ function getPropsForGroupNotification(
     });
   }
 
-  if (groupUpdate.joined) {
+  if (groupUpdate.joined?.length) {
     changes.push({
       type: 'add' as ChangeType,
       contacts: map(
diff --git a/ts/test-electron/models/messages_test.ts b/ts/test-electron/models/messages_test.ts
index c9647b0d04..fcd22c5bcd 100644
--- a/ts/test-electron/models/messages_test.ts
+++ b/ts/test-electron/models/messages_test.ts
@@ -150,7 +150,7 @@ describe('Message', () => {
       let message = messages.add(attributes);
       assert.notOk(isGroupUpdate(message.attributes));
 
-      message = messages.add({ group_update: true });
+      message = messages.add({ group_update: { left: 'You' } });
       assert.ok(isGroupUpdate(message.attributes));
     });
   });