Redeclaration of a Function in the now namespace fails

I declared a function on the client

now.foo = function() { console.log("foo"); };

and I can use it on the server with

user.now.foo();

But, if i redeclare the function in the client

now.foo = function() { console.log("bar"); };

I cannot access it from the server anymore:

TypeError: Property 'foo' of object #

Flotype / now