diff --git a/pysaliency/precomputed_models.py b/pysaliency/precomputed_models.py
index 1c3ba08..a24a460 100644
--- a/pysaliency/precomputed_models.py
+++ b/pysaliency/precomputed_models.py
@@ -101,14 +101,18 @@ def export_model_to_hdf5(model, stimuli, filename, compression=9, overwrite=True
         mode = 'a'
 
     with h5py.File(filename, mode=mode) as f:
-        for k, s in enumerate(tqdm(stimuli)):
-            if not overwrite and names[k] in f:
-                logging.debug(f"Skipping already existing entry {names[k]}")
-                continue
+        if overwrite:
+            indices = range(len(stimuli))
+        else:
+            indices = [i for i in range(len(stimuli)) if names[i] not in f]
+            logging.debug(f"Skipping {len(stimuli) - len(indices)} already existing entries")
+        for k in tqdm(indices):
+            stimulus = stimuli[k]
+
             if isinstance(model, SaliencyMapModel):
-                smap = model.saliency_map(s)
+                smap = model.saliency_map(stimulus)
             elif isinstance(model, Model):
-                smap = model.log_density(s)
+                smap = model.log_density(stimulus)
             else:
                 raise TypeError(type(model))
             f.create_dataset(names[k], data=smap, compression=compression)