grunt config is missing in tasks using grunt.loadTasks

doxer.js

module.exports = function(grunt) {
  grunt.registerTask("doxer", "Generate docs", function() {
    grunt.log.writeln("generator: " + this.generator); // <-- this.generator is undefined
  });
};

grunt.js

module.exports = function(grunt) {
  grunt.initConfig({
    doxer: {
      generator: "DocGen"
    }
  });

  grunt.loadTasks("tasks");
};