 ExerciseWithScroll = React.createClass
   displayName: 'ExerciseWithScroll'
   mixins: [ScrollListenerMixin, ScrollTrackerParentMixin, ExerciseMixin]
-  wrapPartWithScrollTracker: (exerciseParts, part, index) ->
+  wrapPartWithScroll: (parts, exercisePart, index) ->
+    part = parts[index]
+
     scrollState =
       key: part.stepIndex
       questionNumber: part.questionNumber

      return @renderSinglePart()

    exerciseParts = @renderMultiParts()
    exercisePartsWithScroll = _.map parts, _.partial @wrapPartWithScrollTracker, exerciseParts
    exerciseGroup = @renderGroup()
    footer ?= @renderFooter()


      scrollState={scrollState}
      setScrollPoint={@setScrollPoint}
      unsetScrollPoint={@unsetScrollPoint}>
      {exercisePart}
    </ScrollTracker>

  render: ->
