diff --git a/fastchat/serve/inference.py b/fastchat/serve/inference.py
index 6d155aab7..ef6744df5 100644
--- a/fastchat/serve/inference.py
+++ b/fastchat/serve/inference.py
@@ -94,7 +94,7 @@ def generate_stream(
     if model.config.is_encoder_decoder:
         max_src_len = context_len
     else:  # truncate
-        max_src_len = context_len - max_new_tokens - 1
+        max_src_len = context_len - max_new_tokens
 
     input_ids = input_ids[-max_src_len:]
     output_ids = list(input_ids)