Update property ( Base Type = ThingName) on thing

Hi,

I have a problem about update a property of base type ThingName.

Scenario: 

=> Thing Template  = 'ABC' (contain property 'test' of type string)

=> Thing : 'EFG' contain a property of base type THINGNAME (Thing template : 'ABC') , i name it ABC_1

On the service of thing 'EFG' i want to update the property test 

 this code : me.ABC_1.test ='new value' does not work !

Do you have any idea how to achive this ?

Thank you in advance.