Setting value to lookup field from plugin is firing onchange javascript

Hi All,

I am using CRM 2013.

On the account entity, i have a field PrimaryContact. For this Primary Contact field on change event i have written javascript.

On the post update plugin of account, i am setting value  to primarycontact field. While setting this value from plugin the onchange event of primarycontact is firing. I think this should not happen.

Any one faced similar issue?