diff --git a/tests/helper.py b/tests/helper.py
index add6176ed..ed99dadc6 100644
--- a/tests/helper.py
+++ b/tests/helper.py
@@ -3,13 +3,14 @@
 import contextlib
 import importlib.machinery
 import importlib.util
+import locale
 import os
 import pathlib
 import shutil
 import subprocess
 import time
 import unittest.mock
-from collections.abc import Callable, Generator, Iterator, Sequence, Set
+from collections.abc import Callable, Generator, Iterable, Iterator, Sequence, Set
 from typing import Any
 from unittest.mock import MagicMock
 
@@ -109,6 +110,17 @@ def _id(obj: Any) -> Any:
     return obj
 
 
+@contextlib.contextmanager
+def set_locale(
+    category: int, new_locale: Iterable[str | None] | None
+) -> Generator[None]:
+    """Set locale and restore it after leaving this context manager."""
+    orig_locale = locale.getlocale(category)
+    locale.setlocale(category, new_locale)
+    yield
+    locale.setlocale(category, orig_locale)
+
+
 def skip_if_command_is_missing(cmd: str) -> Callable:
     """Skip a test if the command is not found."""
     if shutil.which(cmd) is None:
diff --git a/tests/system/test_packaging_apt_dpkg.py b/tests/system/test_packaging_apt_dpkg.py
index 19d25cb3b..4a62c609d 100644
--- a/tests/system/test_packaging_apt_dpkg.py
+++ b/tests/system/test_packaging_apt_dpkg.py
@@ -4,6 +4,7 @@
 
 import glob
 import gzip
+import locale
 import os
 import pathlib
 import shutil
@@ -17,6 +18,7 @@
 import pytest
 
 from apport.packaging_impl.apt_dpkg import _parse_deb822_sources, impl
+from tests.helper import set_locale
 from tests.paths import get_test_data_directory
 
 if shutil.which("dpkg") is None:
@@ -347,6 +349,7 @@ def test_install_packages_system(
 
 
 @pytest.mark.requires_internet
+@set_locale(locale.LC_MESSAGES, "C.UTF-8")
 def test_install_packages_error(
     configdir: str, cachedir: str, rootdir: str, apt_style: AptStyle
 ) -> None: