diff --git a/PDP10/pdp10_lp20.c b/PDP10/pdp10_lp20.c
index 02e9d47c..912a7017 100644
--- a/PDP10/pdp10_lp20.c
+++ b/PDP10/pdp10_lp20.c
@@ -998,7 +998,7 @@ return reason;
  * So u3 contains the number of seconds desired, and u4 the number to go.
  */
 static void set_flush_timer (UNIT *uptr) {
-uptr = (UNIT *)uptr->up7;
+uptr = lp20_unit+1;
 uptr->u4 = uptr->u3;
 uptr->u5 = (int32)time(NULL);
 sim_cancel(uptr);
@@ -1011,7 +1011,7 @@ if (--uptr->u4 > 0) {
     sim_activate_after (uptr, uptr->wait);
     return SCPE_OK;
 }
-uptr = (UNIT *)uptr->up7;
+uptr = lp20_unit+1;
 fflush (uptr->fileref);
 return SCPE_OK;
 }