diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index e5a7d4bc..994745f2 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -59,6 +59,7 @@ jobs:
       - name: Setup micromamba
         uses: mamba-org/setup-micromamba@v1
         with:
+          micromamba-version: '2.0.0-0'
           environment-file: devtools/conda-envs/test_env.yaml
           environment-name: openmmtools-test
           create-args: >-