Type of SamplingMedia relationship not correct in MeasuredQuantities

When requesting the list of MeasuredQuantities, the type of the linked SamplingMedia is not correct in the relationships:

      {
         "type":"MeasuredQuantity",
         "id":"1",
         "attributes":{
            "term":"Adsorbable organically bonded halogens (AOX)",
            "definition":null,
            "provenance":null,
            "provenance_uri":null,
            "category":null,
            "note":null,
            "status":"ACCEPTED"
         },
         "relationships":{
            "sampling_medium":{
               "links":{
                  "self":"http://localhost:8000/api/v1/measuredquantities/1/relationships/sampling_medium",
                  "related":"http://localhost:8000/api/v1/measuredquantities/1/sampling_medium/"
               },
               "data":{
                  "type":"GlobalProvenance",
                  "id":"7"
               }
            }
         }
      }

It should be SamplingMedium (or SamplingMedia, as requested in #11 (closed)) instead of GlobalProvenance.