Using Parse Javascript SDK Query GeoPoint inMiles

I am building a Parse application and want all objects to be within a certain distance from one object using GeoPoints. Seems simple, but the following code returns [] (No matches):

app.get('/photos', function(req, res) {

   var Photo = Parse.Object.extend("Photo");

   var query = new Parse.Query(Photo);
   query.equalTo("owner", Parse.User.current());
   query.find({
     success: function(results) {
       // Do something with the returned Parse.Object values
       //res.send(results);
       var photo = results[0];

       // Create a query for places
      var Photo = Parse.Object.extend("Photo");
      var query = new Parse.Query(Photo);
      // Interested in photos taken near this photo.
      query.withinMiles("coordinates", photo.coordinates, 500000);

      // Final list of objects
      query.find({
        success: function(photoObjects) {
           res.send(photoObjects);
        },
        error: function(error) {
         alert("Error: " + error.code + " " + error.message);
        }
      });
     },
     error: function(error) {
       alert("Error: " + error.code + " " + error.message);
     }
   });
});

      

        
        
        
      

    

Oddly enough, if I change the line query.withinMiles("coordinates", photo.coordinates, 500000);

to query.near("coordinates", photo.coordinates);

then it works flawlessly and returns all photos (they each have a GeoPoint within 5 miles of everyone else in the sample dataset, so I used a maximum distance of 500,000 to test the extent of the problem).

The problem is that I need to constrain a certain radius and this is what I thought was "inMiles". Any ideas what I might be doing wrong?