Hi,
It's only a friendly warning, nothing wrong with that (it will work), but, why do you use a local defun(ed) function in this situation?, do you really need it in that way? In most cases a Lambda will work perfectly, in this case you don't even need a Lambda or inline function, just a call to prompt and that's it. There are cases in which you may need to encapsulate a function in order to avoid collisions with some other pieces of code, or just for clarity, but this is not the case.
Gaston Nunez