diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index e3e9cbb..7651e53 100755
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -398,7 +398,8 @@
         result = Maildir(path, factory=self._factory)
         maildirfolder_path = os.path.join(path, 'maildirfolder')
         if not os.path.exists(maildirfolder_path):
-            os.close(os.open(maildirfolder_path, os.O_CREAT | os.O_WRONLY))
+            os.close(os.open(maildirfolder_path, os.O_CREAT | os.O_WRONLY,
+                0666))
         return result
 
     def remove_folder(self, folder):
@@ -1900,7 +1901,7 @@
 
 def _create_carefully(path):
     """Create a file if it doesn't exist and open for reading and writing."""
-    fd = os.open(path, os.O_CREAT | os.O_EXCL | os.O_RDWR)
+    fd = os.open(path, os.O_CREAT | os.O_EXCL | os.O_RDWR, 0666)
     try:
         return open(path, 'rb+')
     finally: