diff --git a/tool/sync_default_gems.rb b/tool/sync_default_gems.rb
old mode 100644
new mode 100755
index a04d8ccea3..73cf779d50
--- a/tool/sync_default_gems.rb
+++ b/tool/sync_default_gems.rb
@@ -1,3 +1,4 @@
+#!/usr/bin/env ruby
 # sync upstream github repositories to ruby repository
 
 require 'fileutils'