diff --git a/.github/workflows/python-tests.yml b/.github/workflows/python-tests.yml
index f247a66..f40d808 100644
--- a/.github/workflows/python-tests.yml
+++ b/.github/workflows/python-tests.yml
@@ -28,6 +28,7 @@ jobs:
     - name: setup mamba
       uses: conda-incubator/setup-miniconda@v3
       with:
+        auto-update-conda: true
         python-version: ${{ matrix.python-version }}
         activate-environment: ovito_test
         mamba-version: "*"
@@ -36,18 +37,22 @@ jobs:
     - name: Install python dependencies conda
       if:  matrix.os == 'macos-latest'
       run: |
+        mamba activate ovito_test
         mamba install -y -c conda-forge pytest
         mamba install -y --strict-channel-priority -c https://conda.ovito.org -c conda-forge ovito>=3.9.1
         mamba install -y pytorch pytorch -c pytorch -c conda-forge
     - name: Install python dependencies conda
       if:  matrix.os != 'macos-latest'
       run: |
+        mamba activate ovito_test
         mamba install -y -c conda-forge pytest
         mamba install -y --strict-channel-priority -c https://conda.ovito.org -c conda-forge ovito
         mamba install -y pytorch pytorch-cuda=12.1 -c pytorch -c nvidia -c conda-forge
     - name: Install python dependencies pip
       run: |
+        mamba activate ovito_test
         python -m pip install .
     - name: Test with pytest
       run: |
+        mamba activate ovito_test
         pytest