diff --git a/sys/dev/nmdm/nmdm.c b/sys/dev/nmdm/nmdm.c
index 55468adfd33c..774f1b389779 100644
--- a/sys/dev/nmdm/nmdm.c
+++ b/sys/dev/nmdm/nmdm.c
@@ -206,7 +206,7 @@ nmdmopen(dev, flag, devtype, p)
 		tp->t_ispeed = tp->t_ospeed = TTYDEF_SPEED;
 	} else if (tp->t_state & TS_XCLUDE && suser(p)) {
 		return (EBUSY);
-	} else if (pti->pt_prison != p->p_prison) {
+	} else if (pti->pt_prison != p->p_ucred->cr_prison) {
 		return (EBUSY);
 	}