formatting error with chameleon expression as attribute

[thet]

this:

<input class="form-check-input" type="checkbox" value="" name="enabled" ${python:"checked" if bundle["enabled"] else ''} />

is changed to:

                      <input class="form-check-input"
                             ${python:"checked"=""
                             ''}=""
                             bundle["enabled"]=""
                             else=""
                             if=""
                             name="enabled"
                             type="checkbox"
                             value=""
                      />

It does format correctly for full HTML attributes with a key and value like this:

                      <input class="form-check-input"
                             checked="${python:'checked' if bundle['enabled'] else None}"
                             name="enabled"
                             type="checkbox"
                             value=""
                      />

zpretty version: 3.1.0