diff --git a/tool/rbinstall.rb b/tool/rbinstall.rb
index 6af01d213a..d4c110e66f 100755
--- a/tool/rbinstall.rb
+++ b/tool/rbinstall.rb
@@ -26,7 +26,7 @@ rescue LoadError
 end
 
 STDOUT.sync = true
-File.umask(0222)
+File.umask(077)
 
 def parse_args(argv = ARGV)
   $mantype = 'doc'