Razor CheckBoxFor Rendering in Weird Style

I have a bool property and want to render that property as a checkbox on my view.

<div class="form-group">
    @Html.LabelFor(model => model.Mouse, htmlAttributes: new { @class = "control-label col-md-2" })
    <div class="col-md-10">
        @Html.CheckBoxFor(model => model.Mouse, new { @class = "form-control checkbox" })
    </div>
</div>

The problem is how it renders:

How do I make it look like a normal checkbox? I have checked the html and the type is checkbox, so I don't know.

Any help is appreciated!