An entity name used as a default attribute value, for an attribute that is not specified in the attribute's start tag, must be a non-SGML data entity or a SUBDOC entity.

#0046   Markup Error

ISO 8879, 7.9.4.3

An entity name used as a default attribute value, for an attribute that is not specified in the attribute's start tag, must be a non-SGML data entity or a SUBDOC entity.