Cannot read property 'render' of undefined

Hello! I'm keep getting error rendering my Form: The form is correctly create, i can see my template inside the template property of the form. .render() is also a known function but when it come to run this.profileForm.render();, it give the undefined error.

My init function:

this.testTmp = {
        performance:
                    '<form class="form-horizontal">\
                <h2>Performance</h2>\
                <fieldset data-fields="legPress,chestPress,pushUpsTest"></fieldset>\
                <table class="table table-striped">\
                    <tr>\
                        <th>Stage</th>\
                        <th>Time</th>\
                        <th>Speed</th>\
                        <th>Speed</th>\
                        <th></th>\
                    </tr>\
                    <tr>\
                        <td>1</td>\
                        <td>0-3 mins</td>\
                        <td>1.7 mph</td>\
                        <td>10%</td>\
                        <td><div data-fields="firstname"></div></td>\
                    </tr>\
                    <tr>\
                        <td>5</td>\
                        <td>12-15 mins</td>\
                        <td>5.5 mph</td>\
                        <td>15%</td>\
                        <td><div data-fields="lastname"></div></td>\
                    </tr>\
                </table>\
                <fieldset data-fields="email,address"></fieldset>\
            </form>'
        };
    this.profileForm = new Backbone.Form({
      template: _.template(this.testTmp.performance),
      model: this.model,
      validate: true
    });

and then i render the form in the render function:

                this.profileForm.render();
        $('#testPlaceholder').append(this.profileForm.el);

i'm using dustjs template but as you see right now i just save my custom template in a variable.

I search everywhere and try thousend different possible solution but whenever i try to use the custom template, i got Cannot read property 'render' of undefined it might not be the best place to ask for help, but i'm kind of lost. If you know better place where i should write, please let me know (Already try in SO without luck) Maybe someone can help me here?

powmedia / backbone-forms

Cannot read property 'render' of undefined #536