diff --git a/packages/backend/src/core/entities/UserEntityService.ts b/packages/backend/src/core/entities/UserEntityService.ts
index 2c67cb772b..6678f9a8a9 100644
--- a/packages/backend/src/core/entities/UserEntityService.ts
+++ b/packages/backend/src/core/entities/UserEntityService.ts
@@ -369,7 +369,7 @@ export class UserEntityService implements OnModuleInit {
 			...(opts.detail ? {
 				url: profile!.url,
 				uri: user.uri,
-				movedToUri: user.movedToUri ? await this.apPersonService.resolvePerson(user.movedToUri) : null,
+				movedToUri: user.movedToUri ? this.apPersonService.resolvePerson(user.movedToUri).then(user => user.uri).catch(() => null) : null,
 				alsoKnownAs: user.alsoKnownAs,
 				createdAt: user.createdAt.toISOString(),
 				updatedAt: user.updatedAt ? user.updatedAt.toISOString() : null,
diff --git a/packages/backend/src/server/api/endpoints/i/known-as.ts b/packages/backend/src/server/api/endpoints/i/known-as.ts
index dc96e5e2eb..d63e4a9716 100644
--- a/packages/backend/src/server/api/endpoints/i/known-as.ts
+++ b/packages/backend/src/server/api/endpoints/i/known-as.ts
@@ -32,6 +32,11 @@ export const meta = {
 			code: 'URI_NULL',
 			id: 'bf326f31-d430-4f97-9933-5d61e4d48a23',
 		},
+		forbiddenToSetYourself: {
+			message: 'You can\'t set yourself as your own alias.',
+			code: 'FORBIDDEN_TO_SET_YOURSELF',
+			id: '25c90186-4ab0-49c8-9bba-a1fa6c202ba4',
+		},
 	},
 } as const;
 
@@ -51,9 +56,6 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 		private accountMoveService: AccountMoveService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
-			// Check parameter
-			if (!ps.alsoKnownAs) throw new ApiError(meta.errors.noSuchUser);
-
 			let unfiltered = ps.alsoKnownAs;
 			const updates = {} as Partial<User>;
 
@@ -71,6 +73,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> {
 					this.apiLoggerService.logger.warn(`failed to resolve dstination user: ${e}`);
 					throw new ApiError(meta.errors.noSuchUser);
 				});
+				if (knownAs.id === me.id) throw new ApiError(meta.errors.forbiddenToSetYourself);
 
 				const toUrl = this.accountMoveService.getUserUri(knownAs);
 				if (!toUrl) throw new ApiError(meta.errors.uriNull);
diff --git a/packages/backend/test/e2e/move.ts b/packages/backend/test/e2e/move.ts
index 7330d50ef3..ee478dea0c 100644
--- a/packages/backend/test/e2e/move.ts
+++ b/packages/backend/test/e2e/move.ts
@@ -54,6 +54,49 @@ describe('Account Move', () => {
 			await Users.update(bob.id, { alsoKnownAs: null });
 		}, 1000 * 10);
 
+		test('Able to create an alias', async () => {
+			await api('/i/known-as', {
+				alsoKnownAs: `@alice@${url.hostname}`,
+			}, bob);
+
+			const newBob = await Users.findOneByOrFail({ id: bob.id });
+			assert.strictEqual(newBob.alsoKnownAs?.length, 1);
+			assert.strictEqual(newBob.alsoKnownAs[0], `${url.origin}/users/${alice.id}`);
+		});
+
+		test('Able to set remote user (but may fail)', async () => {
+			const res = await api('/i/known-as', {
+				alsoKnownAs: `@syuilo@example.com`,
+			}, bob);
+
+			assert.strictEqual(res.status, 400);
+			assert.strictEqual(res.body.error.code, 'NO_SUCH_USER');
+			assert.strictEqual(res.body.error.id, 'fcd2eef9-a9b2-4c4f-8624-038099e90aa5');
+		});
+
+		test('Nothing happen when alias duplicated', async () => {
+			await api('/i/known-as', {
+				alsoKnownAs: `@alice@${url.hostname}`,
+			}, bob);
+			await api('/i/known-as', {
+				alsoKnownAs: `@alice@${url.hostname}`,
+			}, bob);
+
+			const newBob = await Users.findOneByOrFail({ id: bob.id });
+			assert.strictEqual(newBob.alsoKnownAs?.length, 1);
+			assert.strictEqual(newBob.alsoKnownAs[0], `${url.origin}/users/${alice.id}`);
+		});
+
+		test('Unable to add itself', async () => {
+			const res = await api('/i/known-as', {
+				alsoKnownAs: `@bob@${url.hostname}`,
+			}, bob);
+
+			assert.strictEqual(res.status, 400);
+			assert.strictEqual(res.body.error.code, 'FORBIDDEN_TO_SET_YOURSELF');
+			assert.strictEqual(res.body.error.id, '25c90186-4ab0-49c8-9bba-a1fa6c202ba4');
+		});
+
 		test('Unable to add a nonexisting local account to alsoKnownAs', async () => {
 			const res = await api('/i/known-as', {
 				alsoKnownAs: `@nonexist@${url.hostname}`,
@@ -72,10 +115,10 @@ describe('Account Move', () => {
 				alsoKnownAs: `@carol@${url.hostname}`,
 			}, bob);
 
-			const newAlice = await Users.findOneByOrFail({ id: bob.id });
-			assert.strictEqual(newAlice.alsoKnownAs?.length, 2);
-			assert.strictEqual(newAlice.alsoKnownAs[0], `${url.origin}/users/${alice.id}`);
-			assert.strictEqual(newAlice.alsoKnownAs[1], `${url.origin}/users/${carol.id}`);
+			const newBob = await Users.findOneByOrFail({ id: bob.id });
+			assert.strictEqual(newBob.alsoKnownAs?.length, 2);
+			assert.strictEqual(newBob.alsoKnownAs[0], `${url.origin}/users/${alice.id}`);
+			assert.strictEqual(newBob.alsoKnownAs[1], `${url.origin}/users/${carol.id}`);
 		});
 
 		test('Unable to create an alias without the second @', async () => {
@@ -95,7 +138,7 @@ describe('Account Move', () => {
 			assert.strictEqual(res2.body.error.code, 'NO_SUCH_USER');
 			assert.strictEqual(res2.body.error.id, 'fcd2eef9-a9b2-4c4f-8624-038099e90aa5');
 		});
-	})
+	});
 
 	describe('Local to Local', () => {
 		let antennaId = '';
diff --git a/packages/misskey-js/src/entities.ts b/packages/misskey-js/src/entities.ts
index 34857f431f..9efc062eac 100644
--- a/packages/misskey-js/src/entities.ts
+++ b/packages/misskey-js/src/entities.ts
@@ -15,7 +15,6 @@ export type UserLite = {
 	avatarUrl: string;
 	avatarBlurhash: string;
 	alsoKnownAs: string[];
-	movedToUri: any;
 	emojis: {
 		name: string;
 		url: string;
@@ -58,6 +57,7 @@ export type UserDetailed = UserLite & {
 	lang: string | null;
 	lastFetchedAt?: DateString;
 	location: string | null;
+	movedToUri: string;
 	notesCount: number;
 	pinnedNoteIds: ID[];
 	pinnedNotes: Note[];