diff --git a/gns3server/utils/images.py b/gns3server/utils/images.py
index 6fb79f35..72498a82 100644
--- a/gns3server/utils/images.py
+++ b/gns3server/utils/images.py
@@ -20,7 +20,7 @@ import hashlib
 
 from ..config import Config
 from . import force_unix_path
-
+from io import DEFAULT_BUFFER_SIZE
 
 import logging
 log = logging.getLogger(__name__)
@@ -173,7 +173,7 @@ def md5sum(path, stopped_event=None):
                 if stopped_event is not None and stopped_event.is_set():
                     log.error("MD5 sum calculation of `{}` has stopped due to cancellation".format(path))
                     return
-                buf = f.read(128)
+                buf = f.read(DEFAULT_BUFFER_SIZE)
                 if not buf:
                     break
                 m.update(buf)