diff --git a/.github/workflows/test-openmm-rc.yml b/.github/workflows/test-openmm-rc.yml
index 1d14fb5fb..f23fc8273 100644
--- a/.github/workflows/test-openmm-rc.yml
+++ b/.github/workflows/test-openmm-rc.yml
@@ -25,7 +25,10 @@ jobs:
           auto-update-conda: true
       - name: "Install requirements"
         run: |
-          CONDA_PY=$(python -c "import sys; print('.'.join(str(s) for s in sys.version_info[:2]))")
+          # we'd rather use the default Python version, but for now need to
+          # pin to 3.9 (see openpathsampling/openpathsampling#1093)
+          #CONDA_PY=$(python -c "import sys; print('.'.join(str(s) for s in sys.version_info[:2]))")
+          export CONDA_PY=3.9
           echo "Python version: ${CONDA_PY}"
           source devtools/conda_install_reqs.sh
       - name: "Install OpenMM RC"