--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -802,6 +802,10 @@ static int snd_seq_deliver_event(struct snd_seq_client *client, struct snd_seq_e
                return -EMLINK;
        }
 
+       if (snd_seq_ev_is_variable(event) &&
+           atomic && (event->data.ext.len & SNDRV_SEQ_EXT_USRPTR))
+               BUG();
+
        if (event->queue == SNDRV_SEQ_ADDRESS_SUBSCRIBERS ||
            event->dest.client == SNDRV_SEQ_ADDRESS_SUBSCRIBERS)
                result = deliver_to_subscribers(client, event, atomic, hop);