diff --git a/src/os.rs b/src/os.rs
index 3fd0128..c407ef8 100644
--- a/src/os.rs
+++ b/src/os.rs
@@ -407,7 +407,7 @@
             next_u64(&mut |v| self.fill_bytes(v))
         }
         fn fill_bytes(&mut self, v: &mut [u8]) {
-            for s in v.chunks_mut(fuchsia_zircon::ZX_CPRNG_DRAW_MAX_LEN) {
+            for s in v.chunks_mut(fuchsia_zircon::sys::ZX_CPRNG_DRAW_MAX_LEN) {
                 let mut filled = 0;
                 while filled < s.len() {
                     match fuchsia_zircon::cprng_draw(&mut s[filled..]) {