diff --git a/pmda/test/test_leaflet.py b/pmda/test/test_leaflet.py
index 4e8ac099..cd7153bd 100644
--- a/pmda/test/test_leaflet.py
+++ b/pmda/test/test_leaflet.py
@@ -39,9 +39,11 @@ def correct_values_single_frame(self):
         return [np.arange(1, 2150, 12), np.arange(2521, 4670, 12)]
 
     # XFAIL for 2 jobs needs to be fixed!
-    @pytest.mark.parametrize('n_jobs', (pytest.mark.xfail(-1),
-                                        1,
-                                        pytest.mark.xfail(2)))
+    @pytest.mark.parametrize('n_jobs', [
+        pytest.param(-1, marks=pytest.mark.xfail),
+        1,
+        pytest.param(2, marks=pytest.mark.xfail),
+    ])
     def test_leaflet(self, universe, correct_values, n_jobs):
         lipid_heads = universe.select_atoms("name P and resname POPG")
         universe.trajectory.rewind()
diff --git a/pmda/test/test_util.py b/pmda/test/test_util.py
index a8aea221..5ad6524c 100644
--- a/pmda/test/test_util.py
+++ b/pmda/test/test_util.py
@@ -83,7 +83,7 @@ def _test_make_balanced_slices(n_blocks, start, stop, step, scale):
     if n_frames >= n_blocks:
         assert np.all(block_sizes > 0)
         minsize = n_frames // n_blocks
-        assert not np.setdiff1d(block_sizes, [minsize, minsize+1]), \
+        assert len(np.setdiff1d(block_sizes, [minsize, minsize+1])) == 0, \
             "For n_blocks <= n_frames, block sizes are not balanced"
     else:
         # pathological case; we will have blocks with length 0
@@ -91,7 +91,7 @@ def _test_make_balanced_slices(n_blocks, start, stop, step, scale):
         zero_blocks = block_sizes == 0
         assert np.sum(zero_blocks) == n_blocks - n_frames
         assert np.sum(~zero_blocks) == n_frames
-        assert not np.setdiff1d(block_sizes[~zero_blocks], [1]), \
+        assert len(np.setdiff1d(block_sizes[~zero_blocks], [1])) == 0, \
             "For n_blocks>n_frames, some blocks contain != 1 frame"