diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index a5bb9b0..8042672 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -27,6 +27,10 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
 
+    - name: Install tkinter for Ubuntu
+      if: matrix.os == 'ubuntu-latest'
+      run: sudo apt-get install -y python3-tk
+
     - name: Install PDM
       run: python -m pip install pdm==2.13.3
 
diff --git a/tests/conftest.py b/tests/conftest.py
index ee5361d..8526a6e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -5,6 +5,7 @@
 import numpy as np
 import pandas as pd
 import pytest
+from pyoma2.algorithm import SSIcov_algo
 from pyoma2.OMA import BaseSetup, MultiSetup_PoSER, MultiSetup_PreGER, SingleSetup
 
 from .factory import FakeAlgorithm, FakeAlgorithm2, FakeResult, FakeRunParams
@@ -206,8 +207,6 @@ def multi_setup_poser_fixture(
     multi_setup_data_fixture,
 ) -> typing.Generator[MultiSetup_PoSER, None, None]:
     """Fixture for MultiSetup Poser with parameters."""
-    from pyoma2.algorithm import SSIcov_algo
-
     set1, set2, set3, *_ = multi_setup_data_fixture
     ss1 = SingleSetup(set1, fs=100)
     ss2 = SingleSetup(set2, fs=100)