Web Forms :: Button.UseSubmitBehavior Is False Results In JavaScript Error If Mixed With True?

ASP.NET 3.5 SP 1 Following code in ASPX:

<asp:Button
ID="calcShipping"
UseSubmitBehavior="false"
Text="Calc Shipping Costs"
OnClick="calcShipping_Click"
runat="server"
/>
<asp:Button
ID="submit"
runat="server"
Text="Submit Query"
/>

Renders like this in HTML (I find this to be correct):

<input
type="button"
name="calcShipping"
value="Calc Shipping Costs"
onclick="javascript:__doPostBack('calcShipping','')"
id="calcShipping"
/>
<input
type="submit"
name="submit"
value="Submit Query"
id="submit"
/>...........................