diff --git a/async.c b/async.c
index 6930185e64..5b6fe6b4cc 100644
--- a/async.c
+++ b/async.c
@@ -117,15 +117,21 @@ void qemu_bh_schedule_idle(QEMUBH *bh)
 
 void qemu_bh_schedule(QEMUBH *bh)
 {
+    AioContext *ctx;
+
     if (bh->scheduled)
         return;
+    ctx = bh->ctx;
     bh->idle = 0;
-    /* Make sure that idle & any writes needed by the callback are done
-     * before the locations are read in the aio_bh_poll.
+    /* Make sure that:
+     * 1. idle & any writes needed by the callback are done before the
+     *    locations are read in the aio_bh_poll.
+     * 2. ctx is loaded before scheduled is set and the callback has a chance
+     *    to execute.
      */
-    smp_wmb();
+    smp_mb();
     bh->scheduled = 1;
-    aio_notify(bh->ctx);
+    aio_notify(ctx);
 }