diff --git a/scst/src/dev_handlers/scst_vdisk.c b/scst/src/dev_handlers/scst_vdisk.c
index 9ec6e4af6..884f6d827 100644
--- a/scst/src/dev_handlers/scst_vdisk.c
+++ b/scst/src/dev_handlers/scst_vdisk.c
@@ -3269,6 +3269,8 @@ static void fileio_async_complete(struct kiocb *iocb, long ret, long ret2)
 	struct vdisk_cmd_params *p = container_of(iocb, typeof(*p), async.iocb);
 	struct scst_cmd *cmd = p->cmd;
 
+	WARN_ON_ONCE(ret >= 0 && ret != cmd->bufflen);
+
 	if (ret < 0 &&
 	    scst_cmd_get_data_direction(cmd) & SCST_DATA_WRITE)
 		scst_set_cmd_error(cmd,