JqGrid vertical scrollbar

Is it possible for jqGrid to insert a vertical scrollbar instead of increasing its height as it requests new lines from the pager?

My current code is as follows:

$("#grid").jqGrid({
url:'/someUrl',

datatype:"json",
mtype:'GET',
shrinkToFit:true,
forceFit:true,
autowidth:true,
altRows:true,
cellEdit:true,
altclass:'altRowClass',
multiselect:true,
rowNum:15,
height:300,
rowList:[15, 50, 100, 1000],    
rowNum:15    

});