diff --git a/packages/backend/src/core/activitypub/models/ApNoteService.ts b/packages/backend/src/core/activitypub/models/ApNoteService.ts
index 5ca5f6e84..5bbb036e0 100644
--- a/packages/backend/src/core/activitypub/models/ApNoteService.ts
+++ b/packages/backend/src/core/activitypub/models/ApNoteService.ts
@@ -71,7 +71,7 @@ export class ApNoteService {
 	}
 
 	@bindThis
-	public validateNote(object: any, uri: string) {
+	public validateNote(object: IObject, uri: string) {
 		const expectHost = this.utilityService.extractDbHost(uri);
 	
 		if (object == null) {
@@ -85,9 +85,10 @@ export class ApNoteService {
 		if (object.id && this.utilityService.extractDbHost(object.id) !== expectHost) {
 			return new Error(`invalid Note: id has different host. expected: ${expectHost}, actual: ${this.utilityService.extractDbHost(object.id)}`);
 		}
-	
-		if (object.attributedTo && this.utilityService.extractDbHost(getOneApId(object.attributedTo)) !== expectHost) {
-			return new Error(`invalid Note: attributedTo has different host. expected: ${expectHost}, actual: ${this.utilityService.extractDbHost(object.attributedTo)}`);
+
+		const actualHost = object.attributedTo && this.utilityService.extractDbHost(getOneApId(object.attributedTo));
+		if (object.attributedTo && actualHost !== expectHost) {
+			return new Error(`invalid Note: attributedTo has different host. expected: ${expectHost}, actual: ${actualHost}`);
 		}
 	
 		return null;