Gcloud app deploy cannot ignore Dockerfile

I usually deploy my NodeJS app to Google App Engine and ignore all docker assets when deploying by a .gcloudignore file as below:

.git
.gitignore
Dockerfile
docker-compose.yml
nginx/
redis-data/
.vscode/
.DS_Store
.prettierrc
README.md
node_modules/
.env

Last week I have successfully deployed my app to App Engine without any problems. But today (without any changes except source code) it failed and threw me an Error:

ERROR: (gcloud.app.deploy) There is a Dockerfile in the current directory, and the runtime field in /Users/tranphongbb/Works/unstatic/habitify-annual-report-backend/app.yaml is currently set to [runtime: nodejs]. To use your Dockerfile to build a custom runtime, set the runtime field to [runtime: custom]. To continue using the [nodejs] runtime, please remove the Dockerfile from this directory.

Even when removing the .gcloudignore file and go with the skip_files option in app.yaml, it still failed.

My source tree:

.dockerignore
.eslintrc.json
.gcloudignore
.gitignore
.prettierrc
.vscode
Dockerfile
README.md
app.yaml
docker-compose.yml
nginx
package.json
src

Source: Docker Questions