diff --git a/PDP11/pdp11_td.c b/PDP11/pdp11_td.c
index 8eead3f5..71d0fe96 100644
--- a/PDP11/pdp11_td.c
+++ b/PDP11/pdp11_td.c
@@ -702,8 +702,8 @@ static REG td_reg[] = {
     { RDATA  (OFFSET, offset, 16, "offset into current transfer") },
     { RDATA  (UNITNO, unitno, 16, "active unit number") },
 
-    { BRDATAD (IBUF,   td_ctlr[0].ibuf,16, 8, 512, "input buffer"), },
-    { BRDATAD (OBUF,   td_ctlr[0].obuf,16, 8, 512, "output buffer"), },
+    { BRDATAD (IBUF,   td_ctlr[0].ibuf,16, 8, TD_NUMBY+1, "input buffer"), },
+    { BRDATAD (OBUF,   td_ctlr[0].obuf,16, 8, TD_NUMBY+1, "output buffer"), },
     { NULL }
     };