diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index a44b7493..f6764f2e 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -41,7 +41,8 @@ jobs:
         run: |
           python -m pip install --require-hashes -r CI/requirements_ci.txt
       - name: Run linting suite
-        run: tox -e lint
+        run: |
+          python -m tox -e lint
 
   pip:
     name: Test with Python${{ matrix.python-version }} (tox, ${{ matrix.os }}), upstream=${{ matrix.upstream-branch }})
@@ -94,10 +95,10 @@ jobs:
           sudo apt-get install libgdal-dev
       - name: Install GDAL (macOS)
         if: matrix.os == 'macos-latest'
-        uses: tecolicom/actions-use-homebrew-tools@v1
+        uses: tecolicom/actions-use-homebrew-tools@b9c066b79607fa3d71e0be05d7003bb75fd9ff34 # v1.3
         with:
           tools: gdal
-          cache: yes
+          cache: "yes"
       - name: Set GDAL_VERSION (Ubuntu)
         if: matrix.os == 'ubuntu-latest'
         run: |
@@ -167,15 +168,13 @@ jobs:
           environment-file: environment-dev.yml
           create-args: >-
             python=${{ matrix.python-version }}
-      - name: Micromamba version
-        run: |
-          echo "micromamba: $(micromamba --version)"
+          micromamba-version: "1.5.10-0" # pinned to avoid breaking changes with mamba and micromamba (2.0.0).
       - name: Install RavenPy
         run: |
           python -m pip install -e ".[dev,gis]"
       - name: List installed packages
         run: |
-          conda list
+          micromamba list
           python -m pip check || true
       - name: Test RavenPy
         run: |