Operator '+' cannot be used

SCRIPT

#pragma strict

var currentHealth : float = 100;
var maxHealth : int = 100;

var barLength = 0.0;

function Start()
{
	barLength = Screen.width / 8;
}

function Update()
{
	AdjustCurrentHealth (0);
}

function OnGUI()
{
	//Icons for GUI
	GUI.Box(Rect(5, 10, 55, 25), "Health");
	
	//Health
	GUI.Box(Rect(65, 10, 55, 25), currentHealth.ToString("0") + "/" + maxHealth);
}

function AdjustCurrentHealth (adj)
{
	currentHealth += adj;
	
	if(currentHealth >= maxHealth)
	{
		currentHealth = maxHealth;
	}
	
	if(currentHealth <= 0)
	{
		currentHealth = 0;
	}
}

ERROR

Operator ‘+’ cannot be used with a left hand side of type ‘float’ and a right hand side of type ‘Object’.

Can someone tell me what’s wrong with this line

currentHealth += adj;

What should I do?

Modify it to (adj : float) or whatever the right syntax is for JS