diff --git a/CHANGELOG.md b/CHANGELOG.md
index a263680782..1a43649fdb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -53,6 +53,7 @@
 - Fix: ダイレクト投稿の宛先が保存されない問題を修正
 - Fix: Playのページを離れたときに、Playが正常に初期化されない問題を修正
 - Fix: ページのOGP URLが間違っているのを修正
+- Fix: 通知をグループ化している際に、人数が正常に表示されないことがある問題を修正
 
 ### Server
 - Enhance: エンドポイント`antennas/update`の必須項目を`antennaId`のみに
diff --git a/packages/frontend/src/components/MkNotification.vue b/packages/frontend/src/components/MkNotification.vue
index 0d3a5c13ba..73cd7cd5b3 100644
--- a/packages/frontend/src/components/MkNotification.vue
+++ b/packages/frontend/src/components/MkNotification.vue
@@ -58,8 +58,8 @@ SPDX-License-Identifier: AGPL-3.0-only
 			<span v-else-if="notification.type === 'achievementEarned'">{{ i18n.ts._notification.achievementEarned }}</span>
 			<span v-else-if="notification.type === 'test'">{{ i18n.ts._notification.testNotification }}</span>
 			<MkA v-else-if="notification.type === 'follow' || notification.type === 'mention' || notification.type === 'reply' || notification.type === 'renote' || notification.type === 'quote' || notification.type === 'reaction' || notification.type === 'receiveFollowRequest' || notification.type === 'followRequestAccepted'" v-user-preview="notification.user.id" :class="$style.headerName" :to="userPage(notification.user)"><MkUserName :user="notification.user"/></MkA>
-			<span v-else-if="notification.type === 'reaction:grouped' && notification.note.reactionAcceptance === 'likeOnly'">{{ i18n.tsx._notification.likedBySomeUsers({ n: notification.reactions.length }) }}</span>
-			<span v-else-if="notification.type === 'reaction:grouped'">{{ i18n.tsx._notification.reactedBySomeUsers({ n: notification.reactions.length }) }}</span>
+			<span v-else-if="notification.type === 'reaction:grouped' && notification.note.reactionAcceptance === 'likeOnly'">{{ i18n.tsx._notification.likedBySomeUsers({ n: getActualReactedUsersCount(notification) }) }}</span>
+			<span v-else-if="notification.type === 'reaction:grouped'">{{ i18n.tsx._notification.reactedBySomeUsers({ n: getActualReactedUsersCount(notification) }) }}</span>
 			<span v-else-if="notification.type === 'renote:grouped'">{{ i18n.tsx._notification.renotedBySomeUsers({ n: notification.users.length }) }}</span>
 			<span v-else-if="notification.type === 'app'">{{ notification.header }}</span>
 			<MkTime v-if="withTime" :time="notification.createdAt" :class="$style.headerTime"/>
@@ -72,7 +72,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 			</MkA>
 			<MkA v-else-if="notification.type === 'renote' || notification.type === 'renote:grouped'" :class="$style.text" :to="notePage(notification.note)" :title="getNoteSummary(notification.note.renote)">
 				<i class="ti ti-quote" :class="$style.quote"></i>
-				<Mfm :text="getNoteSummary(notification.note.renote)" :plain="true" :nowrap="true" :author="notification.note.renote.user"/>
+				<Mfm :text="getNoteSummary(notification.note.renote)" :plain="true" :nowrap="true" :author="notification.note.renote?.user"/>
 				<i class="ti ti-quote" :class="$style.quote"></i>
 			</MkA>
 			<MkA v-else-if="notification.type === 'reply'" :class="$style.text" :to="notePage(notification.note)" :title="getNoteSummary(notification.note)">
@@ -174,6 +174,11 @@ const rejectFollowRequest = () => {
 	followRequestDone.value = true;
 	misskeyApi('following/requests/reject', { userId: props.notification.user.id });
 };
+
+function getActualReactedUsersCount(notification: Misskey.entities.Notification) {
+	if (notification.type !== 'reaction:grouped') return 0;
+	return new Set(notification.reactions.map((reaction) => reaction.user.id)).size;
+}
 </script>
 
 <style lang="scss" module>