Exam 1z0-750 topic 1 question 44 discussion

Kyle is developing a page with an interactive report, called Employees, using this query:
SELECT EMPNO, ENAME, JOB, DEPTNO FROM EMP WHERE DEPTNO = nvl(:P3_DEPTNO, DEPTNO)
On the page, Kyle adds a select list, called P3_DEPTNO, using this query:
SELECT dname, deptno FROM dept;
He creates a dynamic action on change of P3_DEPTNO, with a true action of "Refresh" against the Employees region.
Kyle then runs the page and selects ACCOUNTING in the P3_DEPTNO item. However, the report still shows employees from all departments.
What must Kyle do to correctly display only employees from the department selected?