hook_theme default arguments not recognised in template
You have to do like

/**
 * Implementation of hook_theme
 */
function my_module_theme() {

return array(

'my_theme' =&gt; array(
  'variables' =&gt; array(
    'var1' =&gt; 'default value',
  ),
  'template' =&gt; 'my-theme',
),


);
}

Instead of arguments use variables.

Hope this will help.