diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 7ffbcc68..26506f22 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -42,32 +42,28 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - name: Set up Python 3.11
-        uses: actions/setup-python@v4
+      - name: Setup Mambaforge
+        uses: conda-incubator/setup-miniconda@v2
         with:
-          python-version: '3.11'
+            miniforge-variant: Mambaforge
+            miniforge-version: latest
+            activate-environment: env
+            use-mamba: true
+      - name: Add conda to system path
+        run: |
+          echo $CONDA/bin >> $GITHUB_PATH
       - name: Install Poetry
         uses: snok/install-poetry@v1
         with:
           version: 1.3.2
-          virtualenvs-create: true
-          virtualenvs-in-project: true
+          virtualenvs-create: false
           installer-parallel: true
       - name: Install dependencies
         run: |
           sudo apt-get install -y libglu1-mesa
+          pip install git+https://github.com/kinnala/scikit-fem.git
           poetry install --no-interaction --no-root
-          source $VENV
-          pip install --upgrade git+https://github.com/kinnala/scikit-fem.git
-      - name: Install slepc4py
-        run: |
-          source $VENV
-          export PETSC_CONFIGURE_OPTIONS="--with-scalar-type=complex"
-          pip install petsc
-          pip install petsc4py
-          pip install slepc
-          pip install slepc4py
+          mamba install slepc4py=*=complex* -y
       - name: Build package
         run: |
-          source $VENV
           poetry build