diff --git a/.github/workflows/ci_tests.yaml b/.github/workflows/ci_tests.yaml
index 7a0003c5985..68b6aa7abec 100644
--- a/.github/workflows/ci_tests.yaml
+++ b/.github/workflows/ci_tests.yaml
@@ -31,7 +31,9 @@ jobs:
           python-version: 3.8
 
       - name: Install packages
-        run: pip install black blackdoc flake8 pylint
+        run: |
+          pip install black blackdoc flake8 pylint
+          sudo apt-get install dos2unix
 
       - name: Formatting check (black and flake8)
         run: make check
@@ -39,6 +41,12 @@ jobs:
       - name: Linting (pylint)
         run: make lint
 
+      - name: Ensure files use UNIX line breaks and have 644 permission
+        run: |
+          find . -type f -not -path '*/\.git/*' -exec grep -Iq . {} \; -exec dos2unix --quiet {} \;
+          find . -type f -not -path '*/\.git/*' -exec grep -Iq . {} \; -exec chmod 644 {} \;
+          if [[ $(git ls-files -m) ]]; then git --no-pager diff HEAD; exit 1; fi
+
   test:
     name: ${{ matrix.os }} - Python ${{ matrix.python-version }}
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/format-command.yml b/.github/workflows/format-command.yml
index c0a320ec204..d1618ce08f9 100644
--- a/.github/workflows/format-command.yml
+++ b/.github/workflows/format-command.yml
@@ -25,12 +25,16 @@ jobs:
 
       # Install formatting tools
       - name: Install formatting tools
-        run: pip install black blackdoc flake8
+        run: |
+          pip install black blackdoc flake8
+          sudo apt-get install dos2unix
 
       # Run "make format" and commit the change to the PR branch
       - name: Commit to the PR branch if any changes
         run: |
           make format
+          find . -type f -not -path '*/\.git/*' -exec grep -Iq . {} \; -exec dos2unix {} \;
+          find . -type f -not -path '*/\.git/*' -exec grep -Iq . {} \; -exec chmod 644 {} \;
           if [[ $(git ls-files -m) ]]; then
             git config --global user.name 'actions-bot'
             git config --global user.email '58130806+actions-bot@users.noreply.github.com'
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index a6ebc260e97..6ba63225274 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -255,6 +255,8 @@ Before committing, run it to automatically format your code:
 make format
 ```
 
+For consistency, we also use UNIX-style line endings (`\n`) and file permission
+644 (`-rw-r--r--`) throughout the whole project.
 Don't worry if you forget to do it. Our continuous integration systems will
 warn us and you can make a new commit with the formatted code.
 Even better, you can just write `/format` in the first line of any comment in a