diff --git a/src/lm_saes/activation/token_source.py b/src/lm_saes/activation/token_source.py
index a215c02..2cb7f5e 100644
--- a/src/lm_saes/activation/token_source.py
+++ b/src/lm_saes/activation/token_source.py
@@ -39,7 +39,7 @@ def fill_with_one_batch(self, batch, pack) -> None:
         if self.is_dataset_tokenized:
             tokens: torch.Tensor = batch["tokens"].to(self.device)
         else:
-            tokens = self.model.to_tokens(batch["text"], prepend_bos=not pack).to(self.device)
+            tokens = self.model.to_tokens(batch["text"], prepend_bos=False).to(self.device)
         if pack:
             while tokens.size(0) > 0:
                 cur_tokens = tokens[0]
@@ -59,7 +59,6 @@ def fill_with_one_batch(self, batch, pack) -> None:
             if tokens.size(1) < self.seq_len:
                 pad_len = self.seq_len - tokens.size(1)
                 tokens = torch.cat([tokens, torch.full((tokens.size(0), pad_len), self.model.tokenizer.pad_token_id, dtype=torch.long, device=self.device)], dim=1)
-
             self.token_buffer = torch.cat([self.token_buffer, tokens], dim=0)