diff --git a/VAX/vax780_bug_history.txt b/VAX/vax780_bug_history.txt
index b4f32f44..f79c0e2f 100644
--- a/VAX/vax780_bug_history.txt
+++ b/VAX/vax780_bug_history.txt
@@ -61,7 +61,7 @@ Bugs Found And Fixed During Simulator Debug
 58. POLYx: add step <does> require truncation (proved by AXE tests).
 59. Unaligned references to IO space: incorrect on CVAX.
 60. REI to compatibility mode: PSL<dv,fu,iv> were not checked for mbz.
-
+61. Indexed immediate not does fault.
 
 
 
diff --git a/VAX/vax780_defs.h b/VAX/vax780_defs.h
index eb162318..d5bc1ca9 100644
--- a/VAX/vax780_defs.h
+++ b/VAX/vax780_defs.h
@@ -1,6 +1,6 @@
 /* vax780_defs.h: VAX 780 model-specific definitions file
 
-   Copyright (c) 2004-2017, Robert M Supnik
+   Copyright (c) 2004-2019, Robert M Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -23,6 +23,7 @@
    used in advertising or otherwise to promote the sale, use or other dealings
    in this Software without prior written authorization from Robert M Supnik.
 
+   23-Apr-19    RMS     Added hook for unpredictable indexed immediate .aw
    18-May-17    RMS     Added model-specific AST validation test
    19-Jan-17    RMS     Moved CR to BR6 (Mark Pizzolato)
    29-Mar-15    RMS     Added model specific IPR max
@@ -151,6 +152,7 @@
 
 #define MT_AST_TEST(r)  r = (r) & 07; \
                         if ((r) > AST_MAX) RSVD_OPND_FAULT
+#define IDX_IMM_TEST
 
 /* Memory */
 
diff --git a/VAX/vax_cpu.c b/VAX/vax_cpu.c
index bbacdbb2..ee349b72 100644
--- a/VAX/vax_cpu.c
+++ b/VAX/vax_cpu.c
@@ -25,6 +25,7 @@
 
    cpu          VAX central processor
 
+   23-Apr-19    RMS     Added hook for unpredictable indexed immediate .aw
    14-Apr-19    RMS     Added hook for non-standard MxPR CC's
    31-Mar-17    RMS     Fixed uninitialized variable on FPD path (COVERITY)
    13-Mar-17    RMS     Fixed dangling else in show_opnd (COVERITY)
@@ -886,20 +887,11 @@ for ( ;; ) {
 
             case AIN|VB:
             case AIN|WB: case AIN|WW: case AIN|WL: case AIN|WQ: case AIN|WO:
-/*              CHECK_FOR_PC; */
                 opnd[j++] = OP_MEM;
             case AIN|AB: case AIN|AW: case AIN|AL: case AIN|AQ: case AIN|AO:
                 va = opnd[j++] = R[rn];
                 if (rn == nPC) {
-                    if (DR_LNT (disp) >= L_QUAD) {
-                        GET_ISTR (temp, L_LONG);
-                        GET_ISTR (temp, L_LONG);
-                        if (DR_LNT (disp) == L_OCTA) {
-                            GET_ISTR (temp, L_LONG);
-                            GET_ISTR (temp, L_LONG);
-                            }
-                        }
-                    else GET_ISTR (temp, DR_LNT (disp));
+                    SETPC (PC + DR_LNT (disp));
                     }
                 else {
                     R[rn] = R[rn] + DR_LNT (disp);
@@ -1410,10 +1402,15 @@ for ( ;; ) {
                     break;
 
                 case AIN:
-                    CHECK_FOR_PC;
                     index = index + R[rn];
-                    R[rn] = R[rn] + DR_LNT (disp);
-                    recq[recqptr++] = RQ_REC (AIN | (disp & DR_LNMASK), rn);
+                    if (rn == nPC) {
+                        IDX_IMM_TEST;
+                        SETPC (PC + DR_LNT (disp));
+                        }
+                    else {
+                        R[rn] = R[rn] + DR_LNT (disp);
+                        recq[recqptr++] = RQ_REC (AIN | (disp & DR_LNMASK), rn);
+                        }
                     break;
 
                 case AID:
diff --git a/VAX/vax_defs.h b/VAX/vax_defs.h
index c8b9f7d5..0d986c3a 100644
--- a/VAX/vax_defs.h
+++ b/VAX/vax_defs.h
@@ -602,7 +602,7 @@ enum opcodes {
 #define STR_GETDPC(x)   (((x) >> STR_V_DPC) & STR_M_DPC)
 #define STR_GETCHR(x)   (((x) >> STR_V_CHR) & STR_M_CHR)
 #define STR_PACK(m,x)   ((((PC - fault_PC) & STR_M_DPC) << STR_V_DPC) | \
-                    (((m) & STR_M_CHR) << STR_V_CHR) | ((x) & STR_LNMASK))
+                        (((m) & STR_M_CHR) << STR_V_CHR) | ((x) & STR_LNMASK))
 
 /* Read and write */
 
diff --git a/VAX/vaxmod_defs.h b/VAX/vaxmod_defs.h
index df8c5209..e096d56b 100644
--- a/VAX/vaxmod_defs.h
+++ b/VAX/vaxmod_defs.h
@@ -1,6 +1,6 @@
 /* vaxmod_defs.h: VAX model-specific definitions file
 
-   Copyright (c) 1998-2017, Robert M Supnik
+   Copyright (c) 1998-2019, Robert M Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -23,6 +23,7 @@
    used in advertising or otherwise to promote the sale, use or other dealings
    in this Software without prior written authorization from Robert M Supnik.
 
+   23-Apr-19    RMS     Added hook for unpredictable indexed immediate .aw
    18-May-17    RMS     Added model-specific AST validation test
    29-Mar-15    RMS     Added model-specific IPR max
    20-Dec-13    RMS     Added prototypes for unaligned IO and register handling
@@ -217,6 +218,7 @@
 #define LP_AST_TEST(r)
 #define LP_MBZ84_TEST(r)
 #define LP_MBZ92_TEST(r)
+#define IDX_IMM_TEST    RSVD_ADDR_FAULT                 /* fault on indexed imm */
 
 #define MT_AST_TEST(r)  if ((r) > AST_MAX) RSVD_OPND_FAULT