MVC6 TagHelper not disabling checkbox

I have written a TagHelper called CanEditTagHelper that disables/enables input controls depending on a value passed in from the view.

The TagHelper looks like this:

[HtmlTargetElement("input", Attributes = CanEditAttribute)]
public class CanEditTagHelper : TagHelper
{
    private const string CanEditAttribute = "asp-can-edit";

    [HtmlAttributeName(CanEditAttribute)]
    public bool CanEdit { set; get; }

    public CanEditTagHelper(IHtmlGenerator generator)
    {
    }

    public override void Process(TagHelperContext context, TagHelperOutput output)
    {
        if (!CanEdit)
        {
            output.Attributes["disabled"] = "disabled";
        }
        base.Process(context, output);
    }
}

And it is used in the view like so...

<input asp-for="UserName" asp-can-edit='Model.CanEditMember("UserName")' />

This works well for regular inputs but doesn't seem to work for CheckBoxes (specifically, bootstrap checkboxes). The disabled attribute is never added to the checkbox input.

<div class="checkbox">
    <label asp-for="Active" asp-context="label">
        <input asp-for="Active" 
               asp-can-edit='Model.CanEditMember("Active")'
               type="checkbox" />
            Active
    </label>
</div>

Does anyone know why this tag helper doesn't add a disabled attribute to checkboxes?