unity2D: make object face mouse

I currently have code working that a game object will follow the mouse (rotating towards it) and it works fine, unless i change the position of the object (using rigidbody2D.velocity).

void Update () {
		Vector3 mouseScreen = Input.mousePosition;
		Vector3 mouse = Camera.main.ScreenToWorldPoint(mouseScreen);

		transform.rotation = Quaternion.Euler(0, 0, Mathf.Atan2(mouse.y, mouse.x) * Mathf.Rad2Deg - 90);
}

Any ideas on what i can change?
Thanks!

It should work if you map the coordinates to local space (not tested):

transform.rotation = Quaternion.Euler(0, 0, Mathf.Atan2(mouse.y - transform.position.y, mouse.x - transform.position.x) * Mathf.Rad2Deg - 90);