diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 58f035a18..1995a9d56 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -22,6 +22,8 @@ jobs:
           - ubuntu-latest
         arch:
           - x64
+    env:              # Don't use system Python (needed by PyCall)
+      PYTHON: ""
     steps:
       - uses: actions/checkout@v2
       - uses: julia-actions/setup-julia@v1