diff --git a/CHANGELOG.md b/CHANGELOG.md
index 888e084c..19a38262 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Set a user-agent for `handle_user_provided_file` #103
+
+### Changed
+
+- Migrate to generic syntax in all std collections #140
+
+### Fixed
+
+- Do not modify the ffmpeg_args in reencode function #144
+
 ## [3.3.0] - 2024-02-14
 
 ### Added
diff --git a/src/zimscraperlib/video/encoding.py b/src/zimscraperlib/video/encoding.py
index 91d3873f..04c45907 100644
--- a/src/zimscraperlib/video/encoding.py
+++ b/src/zimscraperlib/video/encoding.py
@@ -7,6 +7,7 @@
 import shutil
 import subprocess
 import tempfile
+from copy import deepcopy
 from typing import Optional
 
 from zimscraperlib import logger
@@ -19,6 +20,7 @@ def _build_ffmpeg_args(
     ffmpeg_args: list[str],
     threads: Optional[int],
 ) -> list[str]:
+    ffmpeg_args = deepcopy(ffmpeg_args)
     if threads:
         if "-threads" in ffmpeg_args:
             raise AttributeError("Cannot set the number of threads, already set")
diff --git a/tests/video/test_encoding.py b/tests/video/test_encoding.py
index 8f46af9b..9af4e6dc 100644
--- a/tests/video/test_encoding.py
+++ b/tests/video/test_encoding.py
@@ -1,12 +1,14 @@
 from __future__ import annotations
 
 import re
+from copy import deepcopy
 from pathlib import Path
 from typing import Optional
 
 import pytest
 
 from zimscraperlib.video.encoding import _build_ffmpeg_args
+from zimscraperlib.video.presets import VideoWebmLow
 
 
 @pytest.mark.parametrize(
@@ -94,3 +96,17 @@ def test_build_ffmpeg_args(
                 ffmpeg_args=ffmpeg_args,
                 threads=threads,
             )
+
+
+def test_ffmpeg_args_not_modified():
+    """_build_ffmpeg_args hould not alter the original ffmpeg_args"""
+    preset = VideoWebmLow()
+    ffmpeg_args = preset.to_ffmpeg_args()
+    ffmpeg_args_orig = deepcopy(ffmpeg_args)
+    src_path = Path("file1.mp4")
+    tmp_path = Path("file2.mp4")
+
+    _build_ffmpeg_args(
+        src_path=src_path, tmp_path=tmp_path, ffmpeg_args=ffmpeg_args, threads=1
+    )
+    assert ffmpeg_args == ffmpeg_args_orig