diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index a82af21..2d58c9d 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -76,7 +76,7 @@ jobs:
 
       - run: |
           mk python-release owner=libre-embedded \
-                            repo=vcorelib version=3.5.8
+                            repo=vcorelib version=3.5.9
         if: |
           matrix.python-version == '3.12'
           && matrix.system == 'ubuntu-latest'
diff --git a/README.md b/README.md
index 63dc83e..3251f9c 100644
--- a/README.md
+++ b/README.md
@@ -2,11 +2,11 @@
     =====================================
     generator=datazen
     version=3.2.0
-    hash=dbaeb9acd4862195a49803d20ebfca2c
+    hash=3ac333f89dda773bb84100031b12bfcb
     =====================================
 -->
 
-# vcorelib ([3.5.8](https://pypi.org/project/vcorelib/))
+# vcorelib ([3.5.9](https://pypi.org/project/vcorelib/))
 
 [![python](https://img.shields.io/pypi/pyversions/vcorelib.svg)](https://pypi.org/project/vcorelib/)
 ![Build Status](https://github.com/libre-embedded/vcorelib/workflows/Python%20Package/badge.svg)
diff --git a/config b/config
index e1445ac..fdfdd6f 160000
--- a/config
+++ b/config
@@ -1 +1 @@
-Subproject commit e1445ac3705e2dad143a0c85435c00b88e82c857
+Subproject commit fdfdd6f30d1762c519526a288c3d95e19d3d5ed1
diff --git a/local/variables/package.yaml b/local/variables/package.yaml
index 34f98be..36747a2 100644
--- a/local/variables/package.yaml
+++ b/local/variables/package.yaml
@@ -1,4 +1,4 @@
 ---
 major: 3
 minor: 5
-patch: 8
+patch: 9
diff --git a/pyproject.toml b/pyproject.toml
index 4fcaf28..9e393de 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta:__legacy__"
 
 [project]
 name = "vcorelib"
-version = "3.5.8"
+version = "3.5.9"
 description = "A collection of core Python utilities."
 readme = "README.md"
 requires-python = ">=3.12"
diff --git a/tests/io/test_file_writer.py b/tests/io/test_file_writer.py
index aaa8581..805218a 100644
--- a/tests/io/test_file_writer.py
+++ b/tests/io/test_file_writer.py
@@ -25,8 +25,10 @@ def test_file_writer_different():
     with TemporaryDirectory() as tmpdir:
         out = Path(tmpdir, "out.txt")
 
-        with IndentedFileWriter.from_path_if_different(out) as writer:
-            writer.write("test123")
+        with IndentedFileWriter.from_path_if_different(
+            out, preprocessor=lambda _: "test123"
+        ) as writer:
+            writer.write("")
 
         with IndentedFileWriter.from_path_if_different(out) as writer:
             writer.write("test123")
diff --git a/vcorelib/__init__.py b/vcorelib/__init__.py
index d055059..3222e51 100644
--- a/vcorelib/__init__.py
+++ b/vcorelib/__init__.py
@@ -1,7 +1,7 @@
 # =====================================
 # generator=datazen
 # version=3.2.0
-# hash=79d8335d8e342b975f1837d3b60a5d84
+# hash=e578f4b742db011f745a8c05889f784c
 # =====================================
 
 """
@@ -10,7 +10,7 @@
 
 DESCRIPTION = "A collection of core Python utilities."
 PKG_NAME = "vcorelib"
-VERSION = "3.5.8"
+VERSION = "3.5.9"
 
 # vcorelib-specific content.
 DEFAULT_INDENT = 2
diff --git a/vcorelib/io/file_writer.py b/vcorelib/io/file_writer.py
index 430a957..05543f0 100644
--- a/vcorelib/io/file_writer.py
+++ b/vcorelib/io/file_writer.py
@@ -15,7 +15,11 @@
 
 # internal
 from vcorelib import DEFAULT_ENCODING
-from vcorelib.paths.context import tempfile, text_stream_if_different
+from vcorelib.paths.context import (
+    TextPreprocessor,
+    tempfile,
+    text_stream_if_different,
+)
 
 
 class CommentStyle(Enum):
@@ -113,11 +117,17 @@ def from_path(
     @staticmethod
     @contextmanager
     def from_path_if_different(
-        path: Path, space: str = " ", per_indent: int = 1, **kwargs
+        path: Path,
+        space: str = " ",
+        per_indent: int = 1,
+        preprocessor: TextPreprocessor = None,
+        **kwargs,
     ) -> Iterator["IndentedFileWriter"]:
         """Create an instance from a path as a managed context."""
 
-        with text_stream_if_different(path) as stream:
+        with text_stream_if_different(
+            path, preprocessor=preprocessor
+        ) as stream:
             yield IndentedFileWriter(
                 stream, space=space, per_indent=per_indent, **kwargs
             )
diff --git a/vcorelib/paths/context.py b/vcorelib/paths/context.py
index c893a62..80f9b76 100644
--- a/vcorelib/paths/context.py
+++ b/vcorelib/paths/context.py
@@ -9,6 +9,7 @@
 from os import makedirs as _makedirs
 from pathlib import Path as _Path
 from tempfile import NamedTemporaryFile as _NamedTemporaryFile
+from typing import Callable as _Callable
 from typing import Iterator as _Iterator
 from typing import TextIO as _TextIO
 
@@ -118,8 +119,13 @@ def write_text_if_different(path: _Path, data: str) -> bool:
     return do_write
 
 
+TextPreprocessor = _Callable[[str], str]
+
+
 @contextmanager
-def text_stream_if_different(path: _Path) -> _Iterator[_TextIO]:
+def text_stream_if_different(
+    path: _Path, preprocessor: TextPreprocessor = None
+) -> _Iterator[_TextIO]:
     """
     Writes the contents of a string stream if it differs from output path
     data.
@@ -131,4 +137,7 @@ def text_stream_if_different(path: _Path) -> _Iterator[_TextIO]:
         finally:
             content = stream.getvalue()
 
+    if preprocessor:
+        content = preprocessor(content)
+
     write_text_if_different(path, content)