diff --git a/blockjob.c b/blockjob.c
index 3a0c49137e..ff9a614531 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -797,11 +797,14 @@ void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
         return;
     }
 
-    job->busy = false;
+    /* We need to leave job->busy set here, because when we have
+     * put a coroutine to 'sleep', we have scheduled it to run in
+     * the future.  We cannot enter that same coroutine again before
+     * it wakes and runs, otherwise we risk double-entry or entry after
+     * completion. */
     if (!block_job_should_pause(job)) {
         co_aio_sleep_ns(blk_get_aio_context(job->blk), type, ns);
     }
-    job->busy = true;
 
     block_job_pause_point(job);
 }
diff --git a/include/block/blockjob_int.h b/include/block/blockjob_int.h
index f13ad05c0d..43f3be2965 100644
--- a/include/block/blockjob_int.h
+++ b/include/block/blockjob_int.h
@@ -143,7 +143,8 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
  * @ns: How many nanoseconds to stop for.
  *
  * Put the job to sleep (assuming that it wasn't canceled) for @ns
- * nanoseconds.  Canceling the job will interrupt the wait immediately.
+ * nanoseconds.  Canceling the job will not interrupt the wait, so the
+ * cancel will not process until the coroutine wakes up.
  */
 void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns);