diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
index 767a5c1..ece6bfe 100644
--- a/.github/workflows/pythonpackage.yml
+++ b/.github/workflows/pythonpackage.yml
@@ -12,10 +12,10 @@
       matrix:
         python-version: [3.9, 3.8]
         r-version: [3.6, release]
-        os: [windows-latest, macOS-latest]
+        os: [windows-latest, macOS-latest, ubuntu-latest]
         exclude:
           - os: macOS-latest
-            python-version: 3.9
+            python-version: 3.8
           - os: macOS-latest
             r-version: 3.6
           - os: windows-latest
@@ -24,7 +24,7 @@
             r-version: 3.6
           - os: ubuntu-latest
             r-version: 3.6
-            python-version: 3.8
+            python-version: 3.9
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}