TypeError: require.config is not a function

I am using require.js as part of a brunch project. This code is throwing the error:

;require.config({ // require.config is not a function
paths: {
   jquery: "lib/jquery",
   underscore: "lib/underscore",
   backbone: "lib/backbone",
   localstorage: "lib/backbone.localStorage"
}
}); 

Does that mean that requirejs is not getting included properly in the project?