diff --git a/tests/core/test_click_types.py b/tests/core/test_click_types.py
new file mode 100644
index 0000000..b50dac1
--- /dev/null
+++ b/tests/core/test_click_types.py
@@ -0,0 +1,33 @@
+"""Tests for SubtitleCodecChoice — notably the ``original`` keep-source sentinel that
+services set via the ``sub_format`` override (must not be rejected as an invalid codec)."""
+
+from __future__ import annotations
+
+import pytest
+
+from unshackle.core.tracks.subtitle import Subtitle
+from unshackle.core.utils.click_types import SubtitleCodecChoice
+
+choice = SubtitleCodecChoice(Subtitle.Codec)
+
+
+@pytest.mark.parametrize("value", ["original", "ORIGINAL", "Original"])
+def test_original_is_kept_as_sentinel(value):
+    assert choice.convert(value) == "original"
+
+
+@pytest.mark.parametrize(
+    "value,expected",
+    [
+        ("srt", Subtitle.Codec.SubRip),
+        ("ass", Subtitle.Codec.SubStationAlphav4),
+        ("vtt", Subtitle.Codec.WebVTT),
+        ("WVTT", Subtitle.Codec.fVTT),
+    ],
+)
+def test_codecs_still_map(value, expected):
+    assert choice.convert(value) == expected
+
+
+def test_empty_is_none():
+    assert choice.convert(None) is None
diff --git a/unshackle/commands/dl.py b/unshackle/commands/dl.py
index 231065d..7dc1e98 100644
--- a/unshackle/commands/dl.py
+++ b/unshackle/commands/dl.py
@@ -20,7 +20,7 @@ from http.cookiejar import CookieJar, MozillaCookieJar
 from itertools import product
 from pathlib import Path
 from threading import Lock
-from typing import Any, Callable, Optional, TypedDict
+from typing import Any, Callable, Optional, TypedDict, Union
 from uuid import UUID
 
 import click
@@ -521,7 +521,7 @@ class dl:
         "--sub-format",
         type=SubtitleCodecChoice(Subtitle.Codec),
         default=None,
-        help="Set Output Subtitle Format, only converting if necessary.",
+        help="Set Output Subtitle Format, only converting if necessary. Use 'original' to keep source format.",
     )
     @click.option("-V", "--video-only", is_flag=True, default=False, help="Only download video tracks.")
     @click.option("-A", "--audio-only", is_flag=True, default=False, help="Only download audio tracks.")
@@ -1110,7 +1110,7 @@ class dl:
         require_subs: list[str],
         forced_subs: bool,
         exact_lang: bool,
-        sub_format: Optional[Subtitle.Codec],
+        sub_format: Optional[Union[Subtitle.Codec, str]],
         video_only: bool,
         audio_only: bool,
         subs_only: bool,
@@ -2369,6 +2369,8 @@ class dl:
 
                 with console.status("Converting Subtitles..."):
                     for subtitle in title.tracks.subtitles:
+                        if sub_format == "original":
+                            continue
                         if sub_format:
                             if subtitle.codec != sub_format:
                                 subtitle.convert(sub_format, forced=True)
diff --git a/unshackle/core/utils/click_types.py b/unshackle/core/utils/click_types.py
index 3ccd5a9..542c380 100644
--- a/unshackle/core/utils/click_types.py
+++ b/unshackle/core/utils/click_types.py
@@ -131,6 +131,8 @@ class SubtitleCodecChoice(click.Choice):
                 if value_lower not in choices:
                     choices.append(value_lower)
 
+        choices.append("original")
+
         self.aliases = aliases
         super().__init__(choices, case_sensitive=False)
 
@@ -138,6 +140,9 @@ class SubtitleCodecChoice(click.Choice):
         if not value:
             return None
 
+        if str(value).lower() == "original":
+            return "original"
+
         # First try to convert using the parent class
         converted_value = super().convert(value, param, ctx)