diff --git a/packages/backend/src/server/api/mastodon/endpoints/account.ts b/packages/backend/src/server/api/mastodon/endpoints/account.ts
index badcbcf75..ad8f5b159 100644
--- a/packages/backend/src/server/api/mastodon/endpoints/account.ts
+++ b/packages/backend/src/server/api/mastodon/endpoints/account.ts
@@ -76,15 +76,15 @@ export function apiAccountMastodon(router: Router): void {
 		}
 	});
 	router.get("/v1/accounts/lookup", async (ctx) => {
-		const BASE_URL = `${ctx.protocol}://${ctx.hostname}`;
-		const accessTokens = ctx.headers.authorization;
-		const client = getClient(BASE_URL, accessTokens);
 		try {
-			const data = await client.search(
-				(ctx.request.query as any).acct,
-				"accounts",
-			);
-			ctx.body = convertAccount(data.data.accounts[0]);
+			const args = normalizeUrlQuery(ctx.query);
+			const user = await UserHelpers.getUserFromAcct(args.acct);
+			if (user === null) {
+				ctx.status = 404;
+				return;
+			}
+			const account = await UserConverter.encode(user);
+			ctx.body = convertAccount(account);
 		} catch (e: any) {
 			console.error(e);
 			console.error(e.response.data);
diff --git a/packages/backend/src/server/api/mastodon/helpers/user.ts b/packages/backend/src/server/api/mastodon/helpers/user.ts
index d7afd9020..ebfb4ecd9 100644
--- a/packages/backend/src/server/api/mastodon/helpers/user.ts
+++ b/packages/backend/src/server/api/mastodon/helpers/user.ts
@@ -33,6 +33,7 @@ import { UserConverter } from "@/server/api/mastodon/converters/user.js";
 import { convertId, IdType } from "@/misc/convert-id.js";
 import acceptFollowRequest from "@/services/following/requests/accept.js";
 import { rejectFollowRequest } from "@/services/following/reject.js";
+import { IsNull } from "typeorm";
 
 export type AccountCache = {
 	locks: AsyncLock;
@@ -136,6 +137,12 @@ export class UserHelpers {
 		return this.getUserRelationshipTo(target.id, localUser.id);
 	}
 
+	public static async getUserFromAcct(acct: string): Promise<User | null> {
+		const split = acct.toLowerCase().split('@');
+		if (split.length > 2) throw new Error('Invalid acct');
+		return Users.findOneBy({usernameLower: split[0], host: split[1] ?? IsNull()});
+	}
+
 	public static async getUserMutes(user: ILocalUser, maxId: string | undefined, sinceId: string | undefined, minId: string | undefined, limit: number = 40, cache: AccountCache = UserHelpers.getFreshAccountCache()): Promise<LinkPaginationObject<MastodonEntity.MutedAccount[]>> {
 		if (limit > 80) limit = 80;