diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index 217a1b255..21fe4bbd9 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -154,7 +154,7 @@ jobs:
             python -m venv venv
             source venv/bin/activate
             which python
-            python -m pip install --no-cache-dir ./fwdpy11*-linux*.whl
+            CPPFLAGS= python -m pip install --no-cache-dir ./fwdpy11*-linux*.whl
             python -m fwdpy11 --includes
             python -c "import fwdpy11;print(fwdpy11.__version__)"
             python -c "import fwdpy11;print(fwdpy11.__file__)"