diff --git a/src/humanize/filesize.py b/src/humanize/filesize.py
index c495fed..3323d5e 100644
--- a/src/humanize/filesize.py
+++ b/src/humanize/filesize.py
@@ -2,9 +2,10 @@
 
 from __future__ import annotations
 
-from math import log
+from math import isfinite, log
 
 from humanize.i18n import _gettext as _
+from humanize.number import _format_not_finite
 
 suffixes = {
     "decimal": (
@@ -88,6 +89,8 @@ def naturalsize(
 
     base = 1024 if (gnu or binary) else 1000
     bytes_ = float(value)
+    if not isfinite(bytes_):
+        return _format_not_finite(bytes_)
     abs_bytes = abs(bytes_)
 
     if abs_bytes == 1 and not gnu:
diff --git a/tests/test_filesize.py b/tests/test_filesize.py
index c3e7386..0b3ecd8 100644
--- a/tests/test_filesize.py
+++ b/tests/test_filesize.py
@@ -93,3 +93,15 @@ def test_naturalsize(test_args: list[int] | list[int | bool], expected: str) ->
         test_args[0] = f"-{test_args[0]}"
 
     assert humanize.naturalsize(*test_args) == "-" + expected
+
+
+@pytest.mark.parametrize(
+    "value, expected",
+    [
+        (float("nan"), "NaN"),
+        (float("inf"), "+Inf"),
+        (float("-inf"), "-Inf"),
+    ],
+)
+def test_naturalsize_not_finite(value: float, expected: str) -> None:
+    assert humanize.naturalsize(value) == expected