diff --git a/asio-sys/src/lib.rs b/asio-sys/src/lib.rs
index b9c4f7a..088a538 100644
--- a/asio-sys/src/lib.rs
+++ b/asio-sys/src/lib.rs
@@ -17,6 +17,7 @@ use std::os::raw::c_double;
use errors::ASIOError;
use std::mem;
use std::sync::{Arc, Mutex};
+use std::sync::atomic::{AtomicUsize, Ordering};
use asio_import as ai;
@@ -33,6 +34,12 @@ lazy_static!{
static ref buffer_callback: Mutex