diff --git a/block/backup.c b/block/backup.c
index 1c535b1ab9..3312476d66 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -287,7 +287,7 @@ static void coroutine_fn backup_run(void *opaque)
                 break;
             }
 
-            /* we need to yield so that qemu_aio_flush() returns.
+            /* we need to yield so that bdrv_drain_all() returns.
              * (without, VM does not reboot)
              */
             if (job->common.speed) {
diff --git a/block/mirror.c b/block/mirror.c
index 65b1718671..d421fceac1 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -475,7 +475,7 @@ static void coroutine_fn mirror_run(void *opaque)
                         (cnt + s->sectors_in_flight) * BDRV_SECTOR_SIZE;
 
         /* Note that even when no rate limit is applied we need to yield
-         * periodically with no pending I/O so that qemu_aio_flush() returns.
+         * periodically with no pending I/O so that bdrv_drain_all() returns.
          * We do so every SLICE_TIME nanoseconds, or when there is an error,
          * or when the source is clean, whichever comes first.
          */