diff --git a/CHANGES.rst b/CHANGES.rst
index fe9d3980c..c036b28e1 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -43,6 +43,7 @@ Fixed
 - Work around a `pathlib.Path.resolve` bug in Python 3.8 and 3.9 on Windows.
   The work-around should be removed when Python 3.8 and 3.9 are no longer supported.
 - Add missing configuration flag for Flynt_.
+- Only split source code lines at Python's universal newlines (LF, CRLF, CR).
 
 
 2.1.1_ - 2024-04-16
diff --git a/constraints-oldest.txt b/constraints-oldest.txt
index 462f7e015..a1ea2bb39 100644
--- a/constraints-oldest.txt
+++ b/constraints-oldest.txt
@@ -4,7 +4,8 @@
 # interpreter and Python ependencies. Keep this up-to-date with minimum
 # versions in `setup.cfg`.
 black==22.3.0
-darkgraylib==2.1.0
+# TODO: change to darkgraylib==2.1.1 when it's released
+darkgraylib @ git+https://github.com/akaihola/darkgraylib@newline-splitting
 defusedxml==0.7.1
 flake8-2020==1.6.1
 flake8-bugbear==22.1.11
diff --git a/setup.cfg b/setup.cfg
index f30182804..472261086 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -28,7 +28,8 @@ package_dir =
 packages = find:
 install_requires =
     # NOTE: remember to keep `constraints-oldest.txt` in sync with these
-    darkgraylib~=2.1.0
+    # TODO: update to darkgraylib~=2.1.1 when released
+    darkgraylib @ git+https://github.com/akaihola/darkgraylib@newline-splitting
     toml>=0.10.0
     typing_extensions>=4.0.1
 # NOTE: remember to keep `.github/workflows/python-package.yml` in sync
diff --git a/src/darker/tests/test_main_drop_changes_on_unedited_lines.py b/src/darker/tests/test_main_drop_changes_on_unedited_lines.py
new file mode 100644
index 000000000..03afffd40
--- /dev/null
+++ b/src/darker/tests/test_main_drop_changes_on_unedited_lines.py
@@ -0,0 +1,65 @@
+"""Tests for `__main__._drop_changes_on_unedited_lines`"""
+
+# pylint: disable=use-dict-literal
+
+from pathlib import Path
+from unittest.mock import Mock
+
+import pytest
+
+from darker.__main__ import _drop_changes_on_unedited_lines
+from darkgraylib.utils import TextDocument
+
+
+@pytest.mark.kwparametrize(
+    dict(
+        content=TextDocument("s =  'reformat'\n"),
+        new_chunks=[(1, ("s =  'reformat'",), ('s = "reformat"',))],
+    ),
+    dict(
+        content=TextDocument('s = "keep"\n'),
+        new_chunks=[(1, ('s = "keep"',), ('s = "keep"',))],
+    ),
+    dict(
+        content=TextDocument("""l1 = "first line"\nl2 =  'second line'\n"""),
+        new_chunks=[
+            (
+                1,
+                ('l1 = "first line"', "l2 =  'second line'"),
+                ('l1 = "first line"', 'l2 = "second line"'),
+            )
+        ],
+    ),
+    dict(
+        content=TextDocument(
+            "# coding: iso-8859-5\n# б\x85б\x86\n", encoding="iso-8859-5"
+        ),
+        new_chunks=[
+            (
+                1,
+                ("# coding: iso-8859-5", "# б\x85б\x86"),
+                ("# coding: iso-8859-5", "# б\x85б\x86"),
+            )
+        ],
+    ),
+)
+def test_unchanged_content(tmp_path, content, new_chunks):
+    """Test that no reformats make it through for unmodified files."""
+    # A mock object that always returns an empty list of changed lines
+    edited_linenums_differ = Mock()
+    edited_linenums_differ.revision_vs_lines = Mock(return_value=[])
+    # The expected result is the same as the input content, unmodified
+    expect = content
+
+    result = _drop_changes_on_unedited_lines(
+        new_chunks,
+        abspath_in_rev2=tmp_path / "file.py",
+        relpath_in_repo=Path("file.py"),
+        edited_linenums_differ=edited_linenums_differ,
+        rev2_content=content,
+        rev2_isorted=content,
+        has_isort_changes=False,
+        has_fstring_changes=False,
+    )
+
+    assert result == expect