diff --git a/holoviews/element/util.py b/holoviews/element/util.py
index 47f38540aa..130be0c0c4 100644
--- a/holoviews/element/util.py
+++ b/holoviews/element/util.py
@@ -25,7 +25,7 @@
 if TYPE_CHECKING:
     from typing import TypeVar
 
-    Array = TypeVar('Array', np.ndarray, pd.api.extensions.ExtensionArray)
+    Array = TypeVar("Array", np.ndarray, pd.api.extensions.ExtensionArray)
 
 
 def split_path(path):
diff --git a/holoviews/tests/plotting/bokeh/test_barplot.py b/holoviews/tests/plotting/bokeh/test_barplot.py
index 3a3a2a9a8b..0b3c68aec1 100644
--- a/holoviews/tests/plotting/bokeh/test_barplot.py
+++ b/holoviews/tests/plotting/bokeh/test_barplot.py
@@ -352,7 +352,10 @@ def test_bars_not_continuous_data_list_custom_width(self):
         assert plot.handles["glyph"].width == 1
 
     def test_bars_categorical_order(self):
-        cells_dtype = pd.CategoricalDtype(pd.array(["~1M", "~10M", "~100M"], dtype="string"), ordered=True)
+        cells_dtype = pd.CategoricalDtype(
+            pd.array(["~1M", "~10M", "~100M"], dtype="string"),
+            ordered=True,
+        )
         df = pd.DataFrame(dict(
             cells=cells_dtype.categories.astype(cells_dtype),
             time=pd.array([2.99, 18.5, 835.2]),
@@ -361,12 +364,12 @@ def test_bars_categorical_order(self):
 
         bars = Bars(df, ["function", "cells"], ["time"])
         plot = bokeh_renderer.get_plot(bars)
-        x_factors = plot.handles['x_range'].factors
+        x_factors = plot.handles["x_range"].factors
 
         np.testing.assert_equal(x_factors, [
-            ('read', np.str_('~1M')),
-            ('read', np.str_('~10M')),
-            ('read', np.str_('~100M')),
+            ("read", "~1M"),
+            ("read", "~10M"),
+            ("read", "~100M"),
         ])
 
     def test_bars_group(self):