diff --git a/mz_prompt_utils.py b/mz_prompt_utils.py
index 6f837db..5e5579f 100644
--- a/mz_prompt_utils.py
+++ b/mz_prompt_utils.py
@@ -425,6 +425,8 @@ class Utils:
         
                     def download_file_thread(response, cache_filepath):
                         block_size = 1024
+                        if end - (start + existing_size) < block_size:
+                            block_size = end - (start + existing_size)
                         with open(cache_filepath, "ab") as file:
                             for data in response.iter_content(block_size):
                                 file.write(data)