diff --git a/package_release.py b/package_release.py
index 85c56a311a2fc2f0c196a34cb7342918dffc8bb4..3c1145b3ba1deae1ae9ed1481908e6c56bef514d 100755
--- a/package_release.py
+++ b/package_release.py
@@ -12,7 +12,7 @@ import alphaplan_fwr
 
 def md5(fname):
     hash_md5 = hashlib.md5()
-    with open(fname, "rb", encoding="utf-8") as f:
+    with open(fname, "rb", encoding=None) as f:
         for chunk in iter(lambda: f.read(4096), b""):
             hash_md5.update(chunk)
     return hash_md5.hexdigest()