Oracle Message LSX-00162 - string ~S is an invalid default for the complex type

ERRORstring ~S is an invalid default for the complex type
CAUSEIf the {content type} is a simple type definition, then the string must be valid with regard to the simple type definition as defined by String Valid (3.14.4). If the {content type} is mixed, then the {content type}s particle must be emptiable as defined by Particle Emptiable (3.9.6). However, one of these conditions was not met, resulting in this error.
ACTIONMake the default string a valid default with regard to the complex type definition.