missing output

[chrand]

The code in the example does not return the output string "My number: 5\n", only the return code 13 (number of bytes?): Clojure 1.6.0, Java HotSpot 64-bit 1.8.0_20-b26

(require '[net.n01se.clojure-jna :as jna])
(jna/invoke Integer c/printf "My number: %d\n" 5)