         defaultValue: ''
         ref: 'text_area'
         onSubmit: @submit
-      _button ["button button-confirm button-small spec-submit", onClick: @submit],
+      _button ["button button-confirm button-small spec-submit",
+               disabled: !@is_valid(),
+               onClick: @submit],
         Factlink.Global.t.post_subcomment
 
 window.ReactSubCommentList = React.createBackboneClass

  getInitialState: ->
    text: ''

  submit: ->
    model = new SubComment
      content: @state.text
      created_by: currentUser.toJSON()

    unless model.isValid()
      FactlinkApp.NotificationCenter.error "Your comment '#{model.get('content')}' is not valid."
      return

    @props.addToCollection.add(model)
    model.save {},
      error: =>

    @refs.text_area.updateText ''

  updateText: (text)->
    @setState text: $.trim(text)

  is_valid: ->
    @model_for_text().isValid()

  render: ->
    R.div className: 'sub-comment-add spec-sub-comments-form',
