diff --git a/tests/test_utils.py b/tests/test_utils.py
index 223667e9..80b7ebf7 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -2021,12 +2021,14 @@ def test_is_sorted(self):
         assert array_.is_sorted(np.array([0]))
         assert not array_.is_sorted(np.array([1, 0]))
         assert not array_.is_sorted(np.array([0, 1, 2, 4, 3]))
+        assert not array_.is_sorted(np.array([0.0, np.nan, 1.0]))
         # nb
         assert array_.is_sorted_nb(np.array([0, 1, 2, 3, 4]))
         assert array_.is_sorted_nb(np.array([0, 1]))
         assert array_.is_sorted_nb(np.array([0]))
         assert not array_.is_sorted_nb(np.array([1, 0]))
         assert not array_.is_sorted_nb(np.array([0, 1, 2, 4, 3]))
+        assert not array_.is_sorted_nb(np.array([0.0, np.nan, 1.0]))
 
     def test_insert_argsort_nb(self):
         a = np.random.uniform(size=1000)
diff --git a/vectorbt/utils/array_.py b/vectorbt/utils/array_.py
index 354034ba..01a3c847 100644
--- a/vectorbt/utils/array_.py
+++ b/vectorbt/utils/array_.py
@@ -18,7 +18,7 @@ def is_sorted(a: tp.Array1d) -> np.bool_:
 def is_sorted_nb(a: tp.Array1d) -> bool:
     """Numba-compiled version of `is_sorted`."""
     for i in range(a.size - 1):
-        if a[i + 1] < a[i]:
+        if not a[i] <= a[i + 1]:
             return False
     return True