diff --git a/src/spikeinterface/postprocessing/template_metrics.py b/src/spikeinterface/postprocessing/template_metrics.py
index 82f55483b4..3f47c505ad 100644
--- a/src/spikeinterface/postprocessing/template_metrics.py
+++ b/src/spikeinterface/postprocessing/template_metrics.py
@@ -41,7 +41,7 @@ class TemplateMetricsCalculator(BaseWaveformExtractorExtension):
     extension_name = "template_metrics"
     min_channels_for_multi_channel_warning = 10
 
-    def __init__(self, waveform_extractor):
+    def __init__(self, waveform_extractor: WaveformExtractor):
         BaseWaveformExtractorExtension.__init__(self, waveform_extractor)
 
     def _set_params(
@@ -212,7 +212,6 @@ def get_extension_function():
 )
 
 
-# TODO: add typing
 def compute_template_metrics(
     waveform_extractor,
     load_if_exists: bool = False,