diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
index ec33295..21165be 100644
--- a/.github/workflows/pythonpackage.yml
+++ b/.github/workflows/pythonpackage.yml
@@ -30,6 +30,10 @@ jobs:
         python -m pip install --upgrade pip
         pip install flake8 pytest tox tox-gh-actions
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
+    - name: Check sorting of imports
+      uses: isort/isort-action@master
+      with:
+        requirementsFiles: "requirements.txt doc/requirements.txt"
     - name: Lint with flake8
       run: |
         # stop the build if there are Python syntax errors or undefined names