     e.target.closest('.project-root-header')
 
   isDragging: (e) ->
-    Boolean e.dataTransfer.getData 'from-root-path'
+    for item in e.dataTransfer.items
+      if item.type is 'from-root-path'
+        return true
+
+    return false
+
+  isAtomTreeViewEvent: (e) ->
+    for item in e.dataTransfer.items
+      if item.type is 'atom-tree-view-event'
+        return true
+
+    return false
 
   getPlaceholder: ->
     unless @placeholderEl

  onDragOver: (e) =>
    return unless @treeView.list.contains(e.target)

    unless e.dataTransfer.getData('atom-tree-view-event') is 'true'
      return

    e.preventDefault()

    {dataTransfer} = e

    # TODO: support dragging folders from the filesystem -- electron needs to add support first
    return unless @isAtomTreeViewEvent(e)

    fromWindowId = parseInt(dataTransfer.getData('from-window-id'))
    fromRootPath  = dataTransfer.getData('from-root-path')
