diff --git a/github/activity_notifications.go b/github/activity_notifications.go
index feb38ea3391..e126199052a 100644
--- a/github/activity_notifications.go
+++ b/github/activity_notifications.go
@@ -186,7 +186,7 @@ func (s *ActivityService) MarkThreadRead(ctx context.Context, id string) (*Respo
 // GitHub API docs: https://docs.github.com/rest/activity/notifications#mark-a-thread-as-done
 //
 //meta:operation DELETE /notifications/threads/{thread_id}
-func (s *ActivityService) MarkThreadDone(ctx context.Context, id int64) (*Response, error) {
+func (s *ActivityService) MarkThreadDone(ctx context.Context, id string) (*Response, error) {
 	u := fmt.Sprintf("notifications/threads/%v", id)
 
 	req, err := s.client.NewRequest("DELETE", u, nil)
diff --git a/github/activity_notifications_test.go b/github/activity_notifications_test.go
index 752eb62baa6..3483a927cf4 100644
--- a/github/activity_notifications_test.go
+++ b/github/activity_notifications_test.go
@@ -255,19 +255,19 @@ func TestActivityService_MarkThreadDone(t *testing.T) {
 	})
 
 	ctx := t.Context()
-	_, err := client.Activity.MarkThreadDone(ctx, 1)
+	_, err := client.Activity.MarkThreadDone(ctx, "1")
 	if err != nil {
 		t.Errorf("Activity.MarkThreadDone returned error: %v", err)
 	}
 
 	const methodName = "MarkThreadDone"
 	testBadOptions(t, methodName, func() (err error) {
-		_, err = client.Activity.MarkThreadDone(ctx, 0)
+		_, err = client.Activity.MarkThreadDone(ctx, "\n")
 		return err
 	})
 
 	testNewRequestAndDoFailure(t, methodName, client, func() (*Response, error) {
-		return client.Activity.MarkThreadDone(ctx, 1)
+		return client.Activity.MarkThreadDone(ctx, "1")
 	})
 }