Cant use foreach in jsp

<z:listbox>
<z:listitem label="${each}" forEach="Monday, Tuesday, Wednesday"/>
</z:listbox>

[4/7/09 15:08:02:887 EEST] 00000027 zkoss         E org.zkoss.jsp.zul.impl.RootTag$MyRichlet service:305 >>javax.servlet.jsp.JspException: javax.servlet.jsp.JspException: javax.servlet.jsp.JspException: java.lang.NullPointerException
>>javax.servlet.jsp.JspException: javax.servlet.jsp.JspException: java.lang.NullPointerException
>>javax.servlet.jsp.JspException: java.lang.NullPointerException
>>java.lang.NullPointerException
>>	at org.zkoss.jsp.zul.impl.LeafTag.setDynamicAttribute(LeafTag.java:246)
>>	at com.ibm._jsp._KalemTanim._jspx_meth_z_listitem_0(_KalemTanim.java:182)
>>	at com.ibm._jsp._KalemTanim.access$26(_KalemTanim.java:174)
>>	at com.ibm._jsp._KalemTanim$_KalemTanimHelper.invoke3(_KalemTanim.java:1649)
>>	at com.ibm._jsp._KalemTanim$_KalemTanimHelper.invoke(_KalemTanim.java:2091)
>>	at org.zkoss.jsp.zul.impl.BranchTag.doTag(BranchTag.java:67)
>>...