diff --git a/configs/default_configs.py b/configs/default_configs.py
index 1c82490..649910e 100644
--- a/configs/default_configs.py
+++ b/configs/default_configs.py
@@ -56,6 +56,7 @@ def get_default_configs():
   data.normalize_sdf = True
   data.meta_path = "PLACEHOLDER" ### metadata for all dataset files
   data.filter_meta_path = "PLACEHOLDER" ### metadata for the list of training samples
+  data.extension = 'pt' ### either 'pt' or 'npy', depending how the data are stored
 
   # model
   config.model = model = ml_collections.ConfigDict()
@@ -85,4 +86,4 @@ def get_default_configs():
   # rendering
   config.render = render = ml_collections.ConfigDict()
 
-  return config
\ No newline at end of file
+  return config