invitations/accept with shortInvitiationUrl fails with wrong validation

The bellow request is with proper data, but fails with msg "Expected the arguments to be of type string , even thought its a string. It also shoudn't be 500 if it wasn't a string.

Request:

Request method:	POST
Request URI:	https://ssi-dev.vereign.com/api-holder/api/v1/invitations/accept
Proxy:			\<none>
Request params:	\<none>
Query params:	\<none>
Form params:	\<none>
Path params:	\<none>
Headers:		X-Client-UserAgent=test framework
Accept=_/_
Content-Type=application/json; charset=UTF-8
Cookies:		\<none>
Multiparts:		\<none>
Body:
{
"shortInvitationUrl": "https://ssi-dev.vereign.com/issuer/invitations/7cf6766c-9c60-4277-8a80-c1781ed9927c"
}

Response:

{
    "statusCode": 500,
    "message": "Expected the arguments to be of type `string`"
}