REST "Create Folder" Duplicate folder error despite non duplicate

[Anonymous]

According to API document, 
"Name has to be unique under the parent folder. " 
http://developers.marketo.com/documentation/asset-api/create-folder/
But This API returns duplicate error when the folder name has not be unique across all folders.
Is this a marketo defect?

For Example

MyFolder -+-Test1
               +-Test2

When I make Test2 under Test1    ==> Dupulicate Error

MyFolder -+-Test1-+-Test2

               +-Test2

Response is
{"requestId":"6b4e#14c8ccf57b7","success":false,"errors":[{"code":"709","message":"Test2 Duplicate folder name"}]}