disappearing tag when using knockoutJS Twitter Bootstrap

disappearing tag when using knockoutJS Twitter Bootstrap

Say I have this simple example of a form
<form class="form-horizontal">
<div class="input-append date form_datetime">
<input size="16" type="text" value="" data-bind="value:
startDate" />
<span class="add-on"><i class="icon-calendar"></i></span>
</div>
<div class="input-append date form_datetime">
<input size="16" type="text" value="" data-bind="value:
endDate" />
<span class="add-on"><i class="icon-calendar"></i></span>
</div>
</form>
When I load the page, bindings and inputs work as expected but the <form>
tags are missing:
<div class="input-append date form_datetime">
<input size="16" type="text" value="" data-bind="value: startDate" />
<span class="add-on"><i class="icon-calendar"></i></span>
</div>
<div class="input-append date form_datetime">
<input size="16" type="text" value="" data-bind="value: endDate" />
<span class="add-on"><i class="icon-calendar"></i></span>
</div>
This causes some bootstrap-related css to not get applied to the form
inputs. Any idea what might cause that?