JSTL if statement always execute as true

I am working with a JSTL and trying to implement a if statement

below is my code for file login.tag

<c:if test="${not empty param.error}">
        //do something
</c:if>

My understanding is when I access this page

with path/index.jsp   //the if statement will not be execute 
with path/index.jsp?error=wrongpassword   //the if statement will be execute

But what I am getting now is the if statement is always execute , Please advice