diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 7a745d0..1874972 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -31,6 +31,7 @@ jobs:
         pytest-version:
           - "pytest<8"
           - "pytest<9"
+          - "pytest<10"
           - "pytest"
           - "git+https://github.com/pytest-dev/pytest.git@main"
         exclude:
diff --git a/pytest_unordered/__init__.py b/pytest_unordered/__init__.py
index 86bdd65..881fd67 100644
--- a/pytest_unordered/__init__.py
+++ b/pytest_unordered/__init__.py
@@ -114,12 +114,16 @@ def pytest_assertrepr_compare(
                     _compare_eq_any(extra_left[0], extra_right[0], verbose=verbose),  # type: ignore[call-arg]
                 )
             else:
+                args = {}
+                if pytest.version_tuple >= (9, 1, 0):
+                    args = {"assertion_text_diff_style": "ndiff"}
                 result.extend(
                     _compare_eq_any(
                         extra_left[0],
                         extra_right[0],
                         highlighter=config.get_terminal_writer()._highlight,  # noqa: SLF001
                         verbose=verbose,
+                        **args,
                     ),
                 )
         else:
diff --git a/tox.ini b/tox.ini
index 68e462e..ac66305 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,7 @@
 [tox]
 envlist =
     {py38,py39}-{pytest7,pytest8},
-    {py310,py311,py312,py313,pypy3}-{pytest7,pytest8,pytestlatest},
+    {py310,py311,py312,py313,pypy3}-{pytest7,pytest8,pytest9,pytestlatest},
     prek
 
 [testenv]
@@ -12,6 +12,7 @@ deps =
   codecov
   pytest7: pytest>=7.4.4,<8
   pytest8: pytest>=8.1.1,<9
+  pytest9: pytest>=9.1,<10
   pytestlatest: pytest
 
 [testenv:prek]