diff --git a/CHANGELOG.md b/CHANGELOG.md
index 23be962d9ed238d4246baca7c7db4f34b8245785..f87fc3a2bb2963799e1e5bb8350c94f5dd42d7df 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 d33b228c3dda89775c43bad6e6a94ade00963937..edfb3aa4fc1e352ad3c94ca1d9c106841c7704aa 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;