diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 45928fd..b0af5b1 100644
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -380,7 +380,7 @@
         }[mode]
         if hasattr(os, "O_BINARY"):
             mode |= os.O_BINARY
-        self.fd = os.open(name, mode)
+        self.fd = os.open(name, mode, 0666)
 
     def close(self):
         os.close(self.fd)