diff --git a/sigma/sigma_bugs.txt b/sigma/sigma_bugs.txt
index 7670884b..594d8a60 100644
--- a/sigma/sigma_bugs.txt
+++ b/sigma/sigma_bugs.txt
@@ -124,7 +124,10 @@
 118. MT: revised error handling failed to set tape mark status on space file forward/reverse.
 119. IO: UEND flag in the wrong bit position in status word.
 120. DP: SEEK(I), RECAL(I) must be coded as fast operations.
-
+121. COC: Transmit long space is 0x6, and stop transmit is 0xE.
+122. COC: Received break generates a data-in channel transaction with a flag bit set
+     in the line number.
+123. DP: dp_inv_adr error must set a TDV visible flag (i.e., PGE) before UEND.
 
 Diagnostic Notes
 ----------------
diff --git a/sigma/sigma_dp.c b/sigma/sigma_dp.c
index e87d22d3..4c9e1e4f 100644
--- a/sigma/sigma_dp.c
+++ b/sigma/sigma_dp.c
@@ -25,6 +25,7 @@
 
    dp           moving head disk pack controller
 
+   09-Dec-22    RMS     Invalid address must set a TDV-visible error flag (Ken Rector)
    23-Jul-22    RMS     SEEK(I), RECAL(I) should be fast operations (Ken Rector)
    02-Jul-22    RMS     Fixed bugs in multi-unit operation
    28-Jun-22    RMS     Fixed off-by-1 error in DP_SEEK definition (Ken Rector)
@@ -771,6 +772,7 @@ switch (uptr->UCMD) {
             return SCPE_OK;
             }
         if (dp_inv_ad (uptr, &da)) {                    /* invalid addr? */
+            ctx->dp_flags |= DPF_PGE;
             chan_uen (dva);                             /* uend */
             return SCPE_OK;
             }
@@ -800,6 +802,7 @@ switch (uptr->UCMD) {
             return SCPE_OK;
             }
         if (dp_inv_ad (uptr, &da)) {                    /* invalid addr? */
+            ctx->dp_flags |= DPF_PGE;
             chan_uen (dva);                             /* uend */
             return SCPE_OK;
             }
@@ -824,6 +827,7 @@ switch (uptr->UCMD) {
 
     case DPS_CHECK:                                     /* write check */
         if (dp_inv_ad (uptr, &da)) {                    /* invalid addr? */
+            ctx->dp_flags |= DPF_PGE;
             chan_uen (dva);                             /* uend */
             return SCPE_OK;
             }
@@ -849,6 +853,7 @@ switch (uptr->UCMD) {
 
     case DPS_READ:                                      /* read */
         if (dp_inv_ad (uptr, &da)) {                    /* invalid addr? */
+            ctx->dp_flags |= DPF_PGE;
             chan_uen (dva);                             /* uend */
                 return SCPE_OK;
             }
@@ -869,6 +874,7 @@ switch (uptr->UCMD) {
 
     case DPS_RHDR:                                      /* read header */
         if (dp_inv_ad (uptr, &da)) {                    /* invalid addr? */
+            ctx->dp_flags |= DPF_PGE;
             chan_uen (dva);                             /* uend */
                 return SCPE_OK;
             }
@@ -994,7 +1000,7 @@ st = 0;
 on_cyl = !sim_is_active (&dp_unit[un + DP_SEEK]) ||
     (dp_unit[un + DP_SEEK].UCMD == DSC_SEEKW);
 if (DP_Q10B (dp_ctx[cidx].dp_ctype))
-    st = ((dp_ctx[cidx].dp_flags & DPF_IVA)? 0x20: 0) |
+    st = ((dp_ctx[cidx].dp_flags & (DPF_IVA|DPF_PGE))? 0x20: 0) |
         (on_cyl? 0x04: 0);
 else st = ((dp_ctx[cidx].dp_flags & DPF_PGE)? 0x20: 0) |
         ((dp_ctx[cidx].dp_flags & DPF_WPE)? 0x08: 0);