MIMEType for excel files (.xlsx) in JCR Node

Hi,

I am trying to create a nt:file node for excel file. I am trying to add property of mimetype as "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet".

But I am getting exception "javax.jcr.nodetype.ConstraintViolationException: No matching property definition: mimeType = application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"

Code : node.setProperty("mimeType", mimeTypeService.getMimeType("xlsx"));

However if I upload an excel file in dam , jcr:content under original node has property "jcr:mimeType" with value "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"

Please provide some pointers.