     newDimensionsAndBackgroundState = state.gutters
     setDimensionsAndBackground(@oldDimensionsAndBackgroundState, newDimensionsAndBackgroundState, @decorationsNode)
 
+    @oldDecorationPositionState ?= {};
     decorationState = state.gutters.customDecorations[@getName()]
 
     updatedDecorationIds = new Set


  # Builds and returns an HTMLElement to represent the specified decoration.
  buildDecorationHTML: (decorationId, decorationInfo) ->
    newNode = document.createElement('div')
    newNode.classList.add('decoration')
    newNode.style.top = decorationInfo.top + 'px'
    newNode.style.height = decorationInfo.height + 'px'
    newNode.style.position = 'absolute'
    if decorationInfo.class
      newNode.classList.add(decorationInfo.class)

        decorationNode.remove()
        delete @decorationNodesById[decorationId]
        delete @decorationItemsById[decorationId]
        delete @oldDecorationPositionState[decorationId]

  ###
  Section: Private Methods
