diff --git a/CHANGELOG.md b/CHANGELOG.md
index 56b25eae2d..c877be07b7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ You should also include the user name that made the change.
 ## 13.x.x (unreleased)
 
 ### Improvements
+- 存在しないカスタム絵文字をテキストで表示するように
 
 ### Bugfixes
 - playを削除する手段がなかったのを修正
diff --git a/packages/backend/src/server/ServerService.ts b/packages/backend/src/server/ServerService.ts
index fac8497b5e..47d11ed0ae 100644
--- a/packages/backend/src/server/ServerService.ts
+++ b/packages/backend/src/server/ServerService.ts
@@ -14,6 +14,7 @@ import { genIdenticon } from '@/misc/gen-identicon.js';
 import { createTemp } from '@/misc/create-temp.js';
 import { UserEntityService } from '@/core/entities/UserEntityService.js';
 import { LoggerService } from '@/core/LoggerService.js';
+import { bindThis } from '@/decorators.js';
 import { ActivityPubServerService } from './ActivityPubServerService.js';
 import { NodeinfoServerService } from './NodeinfoServerService.js';
 import { ApiServerService } from './api/ApiServerService.js';
@@ -22,7 +23,6 @@ import { WellKnownServerService } from './WellKnownServerService.js';
 import { MediaProxyServerService } from './MediaProxyServerService.js';
 import { FileServerService } from './FileServerService.js';
 import { ClientServerService } from './web/ClientServerService.js';
-import { bindThis } from '@/decorators.js';
 
 @Injectable()
 export class ServerService {
@@ -101,7 +101,12 @@ export class ServerService {
 			reply.header('Content-Security-Policy', 'default-src \'none\'; style-src \'unsafe-inline\'');
 
 			if (emoji == null) {
-				return await reply.redirect('/static-assets/emoji-unknown.png');
+				if ('fallback' in request.query) {
+					return await reply.redirect('/static-assets/emoji-unknown.png');
+				} else {
+					reply.code(404);
+					return;
+				}
 			}
 
 			const url = new URL('/proxy/emoji.webp', this.config.url);
diff --git a/packages/frontend/src/components/global/MkEmoji.vue b/packages/frontend/src/components/global/MkEmoji.vue
index bc88cf3be4..b7dd0296cd 100644
--- a/packages/frontend/src/components/global/MkEmoji.vue
+++ b/packages/frontend/src/components/global/MkEmoji.vue
@@ -1,5 +1,6 @@
 <template>
-<img v-if="isCustom" :class="[$style.root, $style.custom, { [$style.normal]: normal, [$style.noStyle]: noStyle }]" :src="url" :alt="alt" :title="alt" decoding="async"/>
+<span v-if="isCustom && errored">:{{ customEmojiName }}:</span>
+<img v-else-if="isCustom" :class="[$style.root, $style.custom, { [$style.normal]: normal, [$style.noStyle]: noStyle }]" :src="url" :alt="alt" :title="alt" decoding="async" @error="errored = true"/>
 <img v-else-if="char && !useOsNativeEmojis" :class="$style.root" :src="url" :alt="alt" decoding="async" @pointerenter="computeTitle"/>
 <span v-else-if="char && useOsNativeEmojis" :alt="alt" @pointerenter="computeTitle">{{ char }}</span>
 <span v-else>{{ emoji }}</span>
@@ -37,6 +38,7 @@ const url = computed(() => {
 	}
 });
 const alt = computed(() => isCustom.value ? `:${customEmojiName}:` : char.value);
+let errored = $ref(false);
 
 // Searching from an array with 2000 items for every emoji felt like too energy-consuming, so I decided to do it lazily on pointerenter
 function computeTitle(event: PointerEvent): void {