diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index f677281..751b65e 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -21,7 +21,7 @@ jobs:
     - name: build new conda env
       run: |
         eval "$(conda shell.bash hook)"
-        conda install -n base mamba -y
+        conda install -n base mamba -y --channel conda-forge
         mamba create -p ./env -y python=${{ matrix.python-version }} --file test-requirements.txt --channel conda-forge --channel bioconda
         conda activate ./env
         pip install -e .