diff --git a/packages/backend/src/core/FetchInstanceMetadataService.ts b/packages/backend/src/core/FetchInstanceMetadataService.ts
index 7f5543620d..54dc925540 100644
--- a/packages/backend/src/core/FetchInstanceMetadataService.ts
+++ b/packages/backend/src/core/FetchInstanceMetadataService.ts
@@ -56,7 +56,8 @@ export class FetchInstanceMetadataService {
 	}
 
 	@bindThis
-	private async tryLock(host: string): Promise<string | null> {
+	// public for test
+	public async tryLock(host: string): Promise<string | null> {
 		// TODO: マイグレーションなのであとで消す (2024.3.1)
 		this.redisClient.del(`fetchInstanceMetadata:mutex:${host}`);
 
@@ -68,7 +69,8 @@ export class FetchInstanceMetadataService {
 	}
 
 	@bindThis
-	private unlock(host: string): Promise<number> {
+	// public for test
+	public unlock(host: string): Promise<number> {
 		return this.redisClient.del(`fetchInstanceMetadata:mutex:v2:${host}`);
 	}
 
@@ -76,13 +78,15 @@ export class FetchInstanceMetadataService {
 	public async fetchInstanceMetadata(instance: MiInstance, force = false): Promise<void> {
 		const host = instance.host;
 
+		// finallyでunlockされてしまうのでtry内でロックチェックをしない
+		// （returnであってもfinallyは実行される）
+		if (!force && await this.tryLock(host) === '1') {
+			// 1が返ってきていたらロックされているという意味なので、何もしない
+			return;
+		}
+
 		try {
 			if (!force) {
-				if (await this.tryLock(host) === '1') {
-					// 1が返ってきていたらロックされている = 何もしない
-					return;
-				}
-
 				const _instance = await this.federatedInstanceService.fetch(host);
 				const now = Date.now();
 				if (_instance && _instance.infoUpdatedAt && (now - _instance.infoUpdatedAt.getTime() < REMOTE_SERVER_CACHE_TTL)) {
diff --git a/packages/backend/test/unit/FetchInstanceMetadataService.ts b/packages/backend/test/unit/FetchInstanceMetadataService.ts
index 510b84b680..bf8f3ab0e3 100644
--- a/packages/backend/test/unit/FetchInstanceMetadataService.ts
+++ b/packages/backend/test/unit/FetchInstanceMetadataService.ts
@@ -56,6 +56,7 @@ describe('FetchInstanceMetadataService', () => {
 				} else if (token === DI.redis) {
 					return mockRedis;
 				}
+				return null;
 			})
 			.compile();
 
@@ -78,6 +79,7 @@ describe('FetchInstanceMetadataService', () => {
 		httpRequestService.getJson.mockImplementation(() => { throw Error(); });
 		const tryLockSpy = jest.spyOn(fetchInstanceMetadataService, 'tryLock');
 		const unlockSpy = jest.spyOn(fetchInstanceMetadataService, 'unlock');
+
 		await fetchInstanceMetadataService.fetchInstanceMetadata({ host: 'example.com' } as any);
 		expect(tryLockSpy).toHaveBeenCalledTimes(1);
 		expect(unlockSpy).toHaveBeenCalledTimes(1);
@@ -92,6 +94,7 @@ describe('FetchInstanceMetadataService', () => {
 		httpRequestService.getJson.mockImplementation(() => { throw Error(); });
 		const tryLockSpy = jest.spyOn(fetchInstanceMetadataService, 'tryLock');
 		const unlockSpy = jest.spyOn(fetchInstanceMetadataService, 'unlock');
+
 		await fetchInstanceMetadataService.fetchInstanceMetadata({ host: 'example.com' } as any);
 		expect(tryLockSpy).toHaveBeenCalledTimes(1);
 		expect(unlockSpy).toHaveBeenCalledTimes(1);
@@ -104,13 +107,30 @@ describe('FetchInstanceMetadataService', () => {
 		const now = Date.now();
 		federatedInstanceService.fetch.mockResolvedValue({ infoUpdatedAt: { getTime: () => now - 10 * 1000 * 60 * 60 * 24 } } as any);
 		httpRequestService.getJson.mockImplementation(() => { throw Error(); });
+		await fetchInstanceMetadataService.tryLock('example.com');
 		const tryLockSpy = jest.spyOn(fetchInstanceMetadataService, 'tryLock');
 		const unlockSpy = jest.spyOn(fetchInstanceMetadataService, 'unlock');
-		await fetchInstanceMetadataService.tryLock('example.com');
+
 		await fetchInstanceMetadataService.fetchInstanceMetadata({ host: 'example.com' } as any);
-		expect(tryLockSpy).toHaveBeenCalledTimes(2);
+		expect(tryLockSpy).toHaveBeenCalledTimes(1);
 		expect(unlockSpy).toHaveBeenCalledTimes(0);
 		expect(federatedInstanceService.fetch).toHaveBeenCalledTimes(0);
 		expect(httpRequestService.getJson).toHaveBeenCalledTimes(0);
 	});
+
+	test('Do when lock not acquired but forced', async () => {
+		redisClient.set = mockRedis();
+		const now = Date.now();
+		federatedInstanceService.fetch.mockResolvedValue({ infoUpdatedAt: { getTime: () => now - 10 * 1000 * 60 * 60 * 24 } } as any);
+		httpRequestService.getJson.mockImplementation(() => { throw Error(); });
+		await fetchInstanceMetadataService.tryLock('example.com');
+		const tryLockSpy = jest.spyOn(fetchInstanceMetadataService, 'tryLock');
+		const unlockSpy = jest.spyOn(fetchInstanceMetadataService, 'unlock');
+
+		await fetchInstanceMetadataService.fetchInstanceMetadata({ host: 'example.com' } as any, true);
+		expect(tryLockSpy).toHaveBeenCalledTimes(0);
+		expect(unlockSpy).toHaveBeenCalledTimes(1);
+		expect(federatedInstanceService.fetch).toHaveBeenCalledTimes(0);
+		expect(httpRequestService.getJson).toHaveBeenCalled();
+	});
 });