diff --git a/.github/workflows/unittests.yml b/.github/workflows/unittests.yml
index 5c70e34..fba6d69 100644
--- a/.github/workflows/unittests.yml
+++ b/.github/workflows/unittests.yml
@@ -69,6 +69,8 @@ jobs:
         if: runner.os == 'macOS'
         run: |
           brew update
+          # Caught by https://github.com/actions/runner-images/issues/6817
+          brew upgrade || true
           brew install --cask xquartz
         shell: bash