diff --git a/packages/backend/test/e2e/fetch-resource.ts b/packages/backend/test/e2e/fetch-resource.ts
index 6aa1798c9a..b85cebf724 100644
--- a/packages/backend/test/e2e/fetch-resource.ts
+++ b/packages/backend/test/e2e/fetch-resource.ts
@@ -44,7 +44,8 @@ describe('Webリソース', () => {
 		const { path, accept, cookie, type } = param;
 		const res = await simpleGet(path, accept, cookie);
 		assert.strictEqual(res.status, 200);
-		assert.strictEqual(res.type?.toLowerCase(), type ?? HTML);
+		// Header values are case-insensitive
+		assert.strictEqual(res.type?.toLowerCase(), (type ?? HTML).toLowerCase());
 		return res;
 	};
 
@@ -95,8 +96,7 @@ describe('Webリソース', () => {
 	describe.each([
 		{ path: '/', type: HTML },
 		{ path: '/docs/ja-JP/about', type: HTML }, // "指定されたURLに該当するページはありませんでした。"
-		// fastify-static gives charset=UTF-8 instead of utf-8 and that's okay
-		{ path: '/api-doc', type: 'text/html; charset=UTF-8' },
+		{ path: '/api-doc', type: HTML },
 		{ path: '/api.json', type: JSON_UTF8 },
 		{ path: '/api-console', type: HTML },
 		{ path: '/_info_card_', type: HTML },