Buildkit ignores .dockerignore in Git repository

When using docker build with a Git repo as build context and DOCKER_BUILDKIT=1 the .dockerignore contents in the Git repo gets ignored and the files/directories get copied in the Docker image.
When DOCKER_BUILDKIT env is not set, the ignored files/directories are correctly excluded and can't be found in the Docker image.

Steps to reproduce the issue:

1. export DOCKER_BUILDKIT=1
2. docker build https://github.com/PHOENIX-MEDIA/buildkit-test.git
3. docker run -ti --rm <image> sh
4. ls -la /var/www/html/
   The files in https://github.com/PHOENIX-MEDIA/buildkit-test/blob/master/.dockerignore shouldn't be in the html folder.

You can repeat the steps with a clone of the repository on your local machine:

1. git clone https://github.com/PHOENIX-MEDIA/buildkit-test.git .
2. docker build .
3. docker run -ti --rm <image> sh
4. ls -la /var/www/html/
   The folder only contains the copy.me file, which is the expected result according to the .dockerignore contents.

I'm using Docker version 19.03.13, build 4484c46d9d on Centos7.