diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 97c4171e758525dd01bf407e312eaf184e569308..0bd20c7b3b2fd66b21723733a9dc5589bd50d4d9 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -4,7 +4,7 @@ stages:
 
 before_script:
   - apt-get update --yes
-  - apt-get install --yes build-essential cmake libfmt-dev pybind11-dev graphviz python3-pyqt5 xvfb
+  - apt-get install --yes build-essential cmake libfmt-dev pybind11-dev graphviz python3-pyqt5 xvfb xdg-utils
   - python -m pip install --upgrade pip
   - python --version
   - pip install pytest pytest-cov sphinx furo numpydoc pytest-xvfb pytest-qt setuptools_scm sphinx-qt-documentation
diff --git a/b_asic/signal_flow_graph.py b/b_asic/signal_flow_graph.py
index 3a99b05176a1c3b5b943b20a12edeeb298f0f94b..d089311c3807a8f134e162094dd7323996f75105 100644
--- a/b_asic/signal_flow_graph.py
+++ b/b_asic/signal_flow_graph.py
@@ -1205,7 +1205,8 @@ class SFG(AbstractOperation):
         """
         dg = Digraph()
         dg.attr(rankdir="LR")
-        dg.engine = 'dot' if engine is None else engine
+        if engine is not None:
+            dg.engine = engine
         for op in self._components_by_id.values():
             if isinstance(op, Signal):
                 if show_id:
@@ -1249,4 +1250,8 @@ class SFG(AbstractOperation):
         """
 
         dg = self.sfg(show_id=show_id)
+        if engine is not None:
+            dg.engine = engine
+        if format is not None:
+            dg.format = format
         dg.view()
diff --git a/test/test_sfg.py b/test/test_sfg.py
index 8c80b85a5f406edc9a3aabcc7a4b0849df062a96..a37caa79850a6f7adac237c68521790424a52a96 100644
--- a/test/test_sfg.py
+++ b/test/test_sfg.py
@@ -1398,9 +1398,9 @@ class TestSFGGraph:
         assert sfg_simple_filter.sfg(show_id=True).source == res
 
     def test_show_sfg_invalid_format(self, sfg_simple_filter):
-        with pytest.raises(AssertionError):
+        with pytest.raises(ValueError):
             sfg_simple_filter.show_sfg(format="ppddff")
 
     def test_show_sfg_invalid_engine(self, sfg_simple_filter):
-        with pytest.raises(AssertionError):
+        with pytest.raises(ValueError):
             sfg_simple_filter.show_sfg(engine="ppddff")