diff --git a/CHANGELOG.md b/CHANGELOG.md
index 23be962d9e..f87fc3a2bb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,8 @@
   [ghsa-gq5q-c77c-v236](https://github.com/misskey-dev/misskey/security/advisories/ghsa-gq5q-c77c-v236)
 - Fix: 招待コードの発行可能な残り数算出に使用すべきロールポリシーの値が違う問題を修正  
   (Cherry-picked from https://activitypub.software/TransFem-org/Sharkey/-/merge_requests/706)
+- Fix: 連合への配信時に、acctの大小文字が区別されてしまい正しくメンションが処理されないことがある問題を修正  
+  (Cherry-picked from https://activitypub.software/TransFem-org/Sharkey/-/merge_requests/711)
 
 ### Misskey.js
 - Fix: Stream初期化時、別途WebSocketを指定する場合の型定義を修正
diff --git a/packages/backend/src/core/MfmService.ts b/packages/backend/src/core/MfmService.ts
index d33b228c3d..edfb3aa4fc 100644
--- a/packages/backend/src/core/MfmService.ts
+++ b/packages/backend/src/core/MfmService.ts
@@ -406,7 +406,7 @@ export class MfmService {
 			mention: (node) => {
 				const a = doc.createElement('a');
 				const { username, host, acct } = node.props;
-				const remoteUserInfo = mentionedRemoteUsers.find(remoteUser => remoteUser.username === username && remoteUser.host === host);
+				const remoteUserInfo = mentionedRemoteUsers.find(remoteUser => remoteUser.username.toLowerCase() === username.toLowerCase() && remoteUser.host?.toLowerCase() === host?.toLowerCase());
 				a.setAttribute('href', remoteUserInfo ? (remoteUserInfo.url ? remoteUserInfo.url : remoteUserInfo.uri) : `${this.config.url}/${acct}`);
 				a.className = 'u-url mention';
 				a.textContent = acct;