diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index b829a52..0abe080 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -121,19 +121,21 @@ jobs:
         with:
           submodules: "true"
 
+      - name: Activate virtualenv
+        run: |
+          . /usr/local/share/venv/bin/activate
+          echo PATH=$PATH >> $GITHUB_ENV
+
       - name: Build package in release
         if: matrix.CODE_COVERAGE == 'OFF'
         run: |
-          python3 -m pip install --upgrade pip        
-          python3 -m pip install cmake numpy matplotlib
-          python3 -m pip install .[dev] --verbose
+          python3 -m pip install .[dev]
 
       - name: Build package in debug for coverage
         if: matrix.CODE_COVERAGE == 'ON'
         run: |
           mkdir build && cd build
-          python3 -m pip install --upgrade pip           
-          python3 -m pip install cmake numpy matplotlib ruff pytest mpi4py 
+          python3 -m pip install numpy matplotlib ruff pytest mpi4py scipy 
           CC=${{ matrix.CC_COMPILER }} CXX=${{ matrix.CXX_COMPILER }} cmake -DUSE_SANITIZER=${{ matrix.USE_SANITIZER }} -DCMAKE_BUILD_TYPE=${{ matrix.CMAKE_BUILD_TYPE }} -DCODE_COVERAGE=${{ matrix.CODE_COVERAGE }} ../
           make
 
@@ -157,7 +159,7 @@ jobs:
 
       - name: Check with ruff
         run: |
-          ruff example/ tests/
+          ruff check example/ tests/
 
       - name: Generate coverage reports
         if: matrix.CODE_COVERAGE == 'ON'
diff --git a/tests/test_ddm_solver.py b/tests/test_ddm_solver.py
index cb730c4..42dcde1 100644
--- a/tests/test_ddm_solver.py
+++ b/tests/test_ddm_solver.py
@@ -4,7 +4,7 @@
 import mpi4py
 import numpy as np
 import pytest
-from conftest import GeneratorFromMatrix, LocalGeneratorFromMatrix
+from conftest import GeneratorFromMatrix
 from scipy.linalg import eig, eigh