diff --git a/io/hpmud/musb.c b/io/hpmud/musb.c
index 755493e..6d9c7fc 100644
--- a/io/hpmud/musb.c
+++ b/io/hpmud/musb.c
@@ -1454,7 +1454,7 @@ enum HPMUD_RESULT __attribute__ ((visibility ("hidden"))) musb_raw_channel_write
BUG("unable to write data %s: %d second io timeout\n", msp->device[pc->dindex].uri, sec_timeout);
}
else
- BUG("unable to write data (len = %d) %s: %m\n", msp->device[pc->dindex].uri, len);
+ BUG("unable to write data (len = %d) %s: %m\n", len, msp->device[pc->dindex].uri);
goto bugout;
}
if(len == 0 && size > 0)