Two functions which call each other recursively

Two functions which call each other recursively

Is it possible to define two functions in clojure which recursively call
each other? For example, this pair:
(defn a [x]
(if (= 0 x) 0 (b (dec x))))
(defn b [x]
(if (= 0 x) 0 (a (dec x))))
Compilation fails with:
Unable to resolve symbol: b in this context
Since I haven't defined b when I try to call it in a.
e.g., in ruby this works fine:
def a(x)
x == 0 ? x : b(x-1)
end
def b(x)
x == 0 ? x : a(x-1)
end