diff --git a/src/spikeinterface/postprocessing/spike_locations.py b/src/spikeinterface/postprocessing/spike_locations.py
index d468bd90ab..96e01a68c4 100644
--- a/src/spikeinterface/postprocessing/spike_locations.py
+++ b/src/spikeinterface/postprocessing/spike_locations.py
@@ -59,9 +59,6 @@ class ComputeSpikeLocations(AnalyzerExtension):
     def __init__(self, sorting_analyzer):
         AnalyzerExtension.__init__(self, sorting_analyzer)
 
-        extremum_channel_inds = get_template_extremum_channel(self.sorting_analyzer, outputs="index")
-        self.spikes = self.sorting_analyzer.sorting.to_spike_vector(extremum_channel_inds=extremum_channel_inds)
-
     def _set_params(
         self,
         ms_before=0.5,
@@ -89,8 +86,9 @@ def _set_params(
     def _select_extension_data(self, unit_ids):
         old_unit_ids = self.sorting_analyzer.unit_ids
         unit_inds = np.flatnonzero(np.isin(old_unit_ids, unit_ids))
+        spikes = self.sorting_analyzer.sorting.to_spike_vector()
 
-        spike_mask = np.isin(self.spikes["unit_index"], unit_inds)
+        spike_mask = np.isin(spikes["unit_index"], unit_inds)
         new_spike_locations = self.data["spike_locations"][spike_mask]
         return dict(spike_locations=new_spike_locations)