diff --git a/lib/iris/tests/unit/concatenate/test__CubeSignature.py b/lib/iris/tests/unit/concatenate/test__CubeSignature.py
index a55140f156..7c8eaa4c2f 100644
--- a/lib/iris/tests/unit/concatenate/test__CubeSignature.py
+++ b/lib/iris/tests/unit/concatenate/test__CubeSignature.py
@@ -19,7 +19,7 @@
 
 
 class Test__coordinate_dim_metadata_equality:
-    @pytest.fixture
+    @pytest.fixture()
     def sample_data(self):
         # Return a standard set of test items, wrapped in a data object
         @dataclass
diff --git a/lib/iris/tests/unit/concatenate/test_concatenate.py b/lib/iris/tests/unit/concatenate/test_concatenate.py
index 577091e9d8..2045c376ce 100644
--- a/lib/iris/tests/unit/concatenate/test_concatenate.py
+++ b/lib/iris/tests/unit/concatenate/test_concatenate.py
@@ -17,7 +17,7 @@
 
 
 class TestEpoch:
-    @pytest.fixture
+    @pytest.fixture()
     def simple_1d_time_cubes(self):
         reftimes = [
             "hours since 1970-01-01 00:00:00",
@@ -49,7 +49,7 @@ def test_concat_1d_with_same_time_units(self, simple_1d_time_cubes):
 
 
 class TestMessages:
-    @pytest.fixture
+    @pytest.fixture()
     def sample_cubes(self):
         # Construct and return a pair of identical cubes
         data = np.arange(24, dtype=np.float32).reshape(2, 3, 4)
@@ -324,7 +324,7 @@ def test_desc_bounds_all_singleton(self):
 
 
 class TestConcatenate__dask:
-    @pytest.fixture
+    @pytest.fixture()
     def sample_lazy_cubes(self):
         # Make a pair of concatenatable cubes, with dim points [1, 2] and [3, 4, 5]
         def build_lazy_cube(points):