Strongloop: currentContext not available in middleware?

I have my middlewares configured in Strongloop in the following way in middleware.json:

{ 
"initial:before": {
      "loopback#favicon": {}
  },
  "initial": {
    "compression": {},
    "cors": {
      "params": {
        "origin": true,
        "credentials": true,
        "maxAge": 86400
      }
    },
    "helmet#xssFilter": {},
    "helmet#frameguard": {
      "params": [
        "deny"
      ]
    },
    "helmet#hsts": {
      "params": {
        "maxAge": 0,
        "includeSubdomains": true
      }
    },
    "helmet#hidePoweredBy": {},
    "helmet#ieNoOpen": {},
    "helmet#noSniff": {},
    "helmet#noCache": {
      "enabled": false
    },
    "express-jwt": {
      "paths": [
        "${restApiRoot}"
      ],
      "params": {
        "secret": "secret"
      }
    }
  },
  "session": {},
  "auth": {
    "./middleware/token-validation": {
      "paths": [
        "${restApiRoot}"
      ]
    }
  },
  "parse": {},
  "routes": {
    "loopback#rest": {
      "paths": [
        "${restApiRoot}"
      ]
    }
  },
  "files": {},
  "final": {
    "loopback#urlNotFound": {}
  },
  "final:after": {
    "loopback#errorHandler": {}
  }
}

This file was genereated by Strongloop, except the "auth" middleware was added manually. In this middleware (token-validation.js) I want to access the currentContext like this:

return function tokenValidation(req, res, next) {
  var app = req.app;
  var ctx = app.loopback.getCurrentContext();
  console.log(ctx);
});

However, the ctx object is always null.... Any ideas?