Can't create folder with REST API in workflow

Hi, i'm using SharePoint Online with O365 subscription. I'm trying to create new folder in list's attachments parent folder using workflow call to REST API like this: https://my-site.sharepoint.com/_api/web/folders/add('/Tickets/Attachments/<ticket lookup id>'), but getting error "can't create folder": {"odata.error":{"code":"-2130247165, Microsoft.SharePoint.SPException","message":{"lang":"ru-RU","value":"Не удается создать папку \"Tickets\/Attachments\/89\"."}}}

Any ideas?..