diff --git a/ogstools/meshlib/mesh_series.py b/ogstools/meshlib/mesh_series.py
index dbbc86706a9bdcea3a0d30936a1d6c8743a27c2a..d43f396541e919545b9263f3cf3650a2d2c620bb 100644
--- a/ogstools/meshlib/mesh_series.py
+++ b/ogstools/meshlib/mesh_series.py
@@ -21,9 +21,7 @@ class MeshSeries:
     """
 
     def __init__(
-        self,
-        filepath: Union[str, Path],
-        time_unit: Optional[Optional[str]] = None,
+        self, filepath: Union[str, Path], time_unit: Optional[str] = "s"
     ) -> None:
         """
         Initialize a MeshSeries object
diff --git a/ogstools/meshplotlib/core.py b/ogstools/meshplotlib/core.py
index 53dc33132a8aa34b800740af9540096dd62c926f..134d156b34e7ffc6a4f5b34a3b1111ffd0f267f2 100644
--- a/ogstools/meshplotlib/core.py
+++ b/ogstools/meshplotlib/core.py
@@ -526,7 +526,7 @@ def plot_probe(
     points: np.ndarray,
     mesh_property: Union[Property, str],
     labels: Optional[list[str]] = None,
-    time_unit: Optional[str] = None,
+    time_unit: Optional[str] = "s",
     interp_method: Optional[Literal["nearest", "linear", "probefilter"]] = None,
     interp_backend_pvd: Optional[Literal["vtk", "scipy"]] = None,
     colors: Optional[list] = None,
@@ -546,7 +546,8 @@ def plot_probe(
                                 `linear` for xdmf MeshSeries and `probefilter`
                                 for pvd MeshSeries.
         :param interp_backend:  Interpolation backend for PVD MeshSeries.
-        :param kwargs:          Keyword arguments passed to the plot function.
+        :param kwargs:          Keyword arguments passed to matplotlib's plot
+                                function.
 
         :returns:   A matplotlib Figure
     """
diff --git a/tests/test_meshplotlib.py b/tests/test_meshplotlib.py
index d75bf6541ebd5fa4f4d4048595653033f89ab401..e74feedaaf4cbbadc882df0a933d64e335385808 100644
--- a/tests/test_meshplotlib.py
+++ b/tests/test_meshplotlib.py
@@ -92,7 +92,6 @@ class MeshplotlibTest(unittest.TestCase):
 
     def test_plot_probe(self):
         """Test creation of probe plots."""
-        setup.reset()
         mesh_series = examples.meshseries_THM_2D
         points = mesh_series.read(0).center
         plot_probe(mesh_series, points, presets.temperature)