diff --git a/lib/instance_agent/platform/linux_util.rb b/lib/instance_agent/platform/linux_util.rb
index 464f0b12..3fbe6999 100644
--- a/lib/instance_agent/platform/linux_util.rb
+++ b/lib/instance_agent/platform/linux_util.rb
@@ -17,7 +17,7 @@ def self.prepare_script_command(script, absolute_cmd_path)
       end
 
       if runas && !sudo
-        return 'su ' + script.runas + ' -c ' + absolute_cmd_path
+        return 'su - ' + script.runas + ' -c ' + absolute_cmd_path
       end
 
       if !runas && sudo