diff --git a/packages/backend/src/core/activitypub/ApRequestService.ts b/packages/backend/src/core/activitypub/ApRequestService.ts
index 69b09ba808..3d1bd44648 100644
--- a/packages/backend/src/core/activitypub/ApRequestService.ts
+++ b/packages/backend/src/core/activitypub/ApRequestService.ts
@@ -203,7 +203,9 @@ export class ApRequestService {
 		});
 
 		//#region リクエスト先がhtmlかつactivity+jsonへのalternate linkタグがあるとき
-		if (res.headers.get('Content-type')?.startsWith('text/html;') && _followAlternate === true) {
+		const contentType = res.headers.get('content-type');
+		
+		if ((contentType === 'text/html' || contentType?.startsWith('text/html;')) && _followAlternate === true) {
 			const html = await res.text();
 			const window = new Window();
 			const document = window.document;