diff --git a/src/humanize/filesize.py b/src/humanize/filesize.py
index fb675fd..f1ef2e3 100644
--- a/src/humanize/filesize.py
+++ b/src/humanize/filesize.py
@@ -4,9 +4,10 @@
 
 __lazy_modules__ = {"humanize.i18n", "math"}
 
-from math import log
+from math import isfinite, log
 
 from humanize.i18n import _gettext as _
+from humanize.number import _format_not_finite
 
 suffixes = {
     "decimal": (
@@ -90,6 +91,10 @@ def naturalsize(
 
     base = 1024 if (gnu or binary) else 1000
     bytes_ = float(value)
+    if not isfinite(bytes_):
+        # Match the rest of the library (see humanize.number): format NaN and
+        # infinities instead of crashing or emitting a bogus suffix like "inf QB".
+        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 e695639..9cea09b 100644
--- a/tests/test_filesize.py
+++ b/tests/test_filesize.py
@@ -4,6 +4,8 @@
 
 from __future__ import annotations
 
+import math
+
 import pytest
 
 import humanize
@@ -103,3 +105,18 @@ 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",
+    [
+        (math.nan, "NaN"),
+        (math.inf, "+Inf"),
+        (-math.inf, "-Inf"),
+        ("nan", "NaN"),
+        ("inf", "+Inf"),
+        ("-inf", "-Inf"),
+    ],
+)
+def test_naturalsize_non_finite(value: float | str, expected: str) -> None:
+    assert humanize.naturalsize(value) == expected