diff --git a/holoviews/core/util.py b/holoviews/core/util.py
index dadba0c088..4b91e612b6 100644
--- a/holoviews/core/util.py
+++ b/holoviews/core/util.py
@@ -2031,7 +2031,9 @@ def is_nan(x):
     Checks whether value is NaN on arbitrary types
     """
     try:
-        return np.isnan(x)
+        # Using pd.isna instead of np.isnan as np.isnan(pd.NA) returns pd.NA!
+        # Call bool() to raise an error if x is pd.NA, an array, etc.
+        return bool(pd.isna(x))
     except Exception:
         return False
 
diff --git a/holoviews/tests/core/test_utils.py b/holoviews/tests/core/test_utils.py
index 560f11245c..41462601d7 100644
--- a/holoviews/tests/core/test_utils.py
+++ b/holoviews/tests/core/test_utils.py
@@ -21,6 +21,7 @@
     dt_to_int,
     find_range,
     get_path,
+    is_nan,
     isfinite,
     make_path_unique,
     max_range,
@@ -806,3 +807,13 @@ def test_unique_array_categorial():
     ser = pd.Series(np.random.choice(["a", "b", "c"], 100)).astype("category")
     res = unique_array([ser])
     assert sorted(res) == ["a", "b", "c"]
+
+
+def test_is_nan():
+    assert is_nan(np.nan) == True
+    assert is_nan(None) == True
+    assert is_nan(pd.NA) == True
+    assert is_nan(pd.NaT) == True
+    assert is_nan([1, 1]) == False
+    assert is_nan([np.nan]) == True
+    assert is_nan([np.nan, np.nan]) == False
diff --git a/holoviews/tests/plotting/bokeh/test_annotationplot.py b/holoviews/tests/plotting/bokeh/test_annotationplot.py
index 4a60a3e823..4520435b2b 100644
--- a/holoviews/tests/plotting/bokeh/test_annotationplot.py
+++ b/holoviews/tests/plotting/bokeh/test_annotationplot.py
@@ -621,3 +621,15 @@ def test_dynamicmap_overlay_hspans(self):
         assert plot_el.handles["x_range"].end == plot_dmap.handles["x_range"].end
         assert plot_el.handles["y_range"].start == plot_dmap.handles["y_range"].start
         assert plot_el.handles["y_range"].end == plot_dmap.handles["y_range"].end
+
+    def test_hspans_no_upper_range(self):
+        # Test for: https://github.com/holoviz/holoviews/issues/6289
+
+        dim = hv.Dimension("p", label="prob", range=(0, None))
+        fig = hv.Curve(
+            [(0, 0.6), (1, 0.3), (2, 0.4), (3, 0.45)], kdims="x", vdims=dim
+        )
+        spans = hv.HSpans([(0, 0.2), (0.4, 0.6)], kdims=["x", dim])
+        plot_el = bokeh_renderer.get_plot(spans * fig)
+        assert plot_el.handles["x_range"].start == 0
+        assert plot_el.handles["x_range"].end == 3