diff --git a/src/spikeinterface/postprocessing/tests/common_extension_tests.py b/src/spikeinterface/postprocessing/tests/common_extension_tests.py
index 8f864e9b84..50e2ecdb57 100644
--- a/src/spikeinterface/postprocessing/tests/common_extension_tests.py
+++ b/src/spikeinterface/postprocessing/tests/common_extension_tests.py
@@ -57,6 +57,7 @@ def setUp(self):
             ms_before=3.0,
             ms_after=4.0,
             max_spikes_per_unit=500,
+            sparse=False,
             n_jobs=1,
             chunk_size=30000,
             overwrite=True,
@@ -92,6 +93,7 @@ def setUp(self):
             ms_before=3.0,
             ms_after=4.0,
             max_spikes_per_unit=500,
+            sparse=False,
             n_jobs=1,
             chunk_size=30000,
             overwrite=True,
@@ -112,6 +114,7 @@ def setUp(self):
             recording,
             sorting,
             mode="memory",
+            sparse=False,
             ms_before=3.0,
             ms_after=4.0,
             max_spikes_per_unit=500,