diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 58d0edbd56..eea3e81de6 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -754,7 +754,8 @@ static void esp_do_nodma(ESPState *s)
     }
 
     if (to_device) {
-        len = MIN(fifo8_num_used(&s->fifo), ESP_FIFO_SZ);
+        len = MIN(s->async_len, ESP_FIFO_SZ);
+        len = MIN(len, fifo8_num_used(&s->fifo));
         esp_fifo_pop_buf(&s->fifo, s->async_buf, len);
         s->async_buf += len;
         s->async_len -= len;