the target property in a ContainerSummeryItem->Mounts->Mount is always null

Mount {#769 ▼
      #target: null
      #source: "/var/www/html"

if I run docker inspect in commandline it shows the correct information

{
   "Type": "bind",
   "Source": "/var/www/html",
   "Target": "/var/www/html"
},

I'm using docker api version 1.39, this might be the issue. is there any way to force the php client to adress the /v1.36 endpoint?