diff --git a/build.py b/build.py
index 8f72d88e..eb83c281 100755
--- a/build.py
+++ b/build.py
@@ -922,7 +922,7 @@ def _setTarItemPerms(tarinfo):
     if tarinfo.isdir():
         tarinfo.mode = 0o755
     else:
-        tarinfo.mode = 0o644
+        tarinfo.mode |= 0o644
     return tarinfo