diff --git a/src/devices/cpu/vax/vaxdasm.cpp b/src/devices/cpu/vax/vaxdasm.cpp
index 8e94057736c..423f5746ebc 100644
--- a/src/devices/cpu/vax/vaxdasm.cpp
+++ b/src/devices/cpu/vax/vaxdasm.cpp
@@ -380,12 +380,12 @@ static const vax_disassembler::opdef s_nonprefix_ops[0x100 - 3] =
 	{ "DIVP"sv,   { mode::rw,   mode::ab,   mode::rw,   mode::ab,   mode::rw,   mode::ab   }, 0 },
 	{ "MOVC3"sv,  { mode::rw,   mode::ab,   mode::ab,   mode::none, mode::none, mode::none }, 0 },
 	{ "CMPC3"sv,  { mode::rw,   mode::ab,   mode::ab,   mode::none, mode::none, mode::none }, 0 },
-	{ "SCANC"sv,  { mode::rw,   mode::ab,   mode::ab,   mode::rb,   mode::none, mode::none }, 0 },
-	{ "SPANC"sv,  { mode::rw,   mode::ab,   mode::ab,   mode::rb,   mode::none, mode::none }, 0 },
-	{ "MOVC5"sv,  { mode::rw,   mode::ab,   mode::rb,   mode::rw,   mode::ab,   mode::none }, 0 },
-	{ "CMPC5"sv,  { mode::rw,   mode::ab,   mode::rb,   mode::rw,   mode::ab,   mode::none }, 0 },
-	{ "MOVTC"sv,  { mode::rw,   mode::ab,   mode::rb,   mode::ab,   mode::rw,   mode::ab   }, 0 },
-	{ "MOVTUC"sv, { mode::rw,   mode::ab,   mode::rb,   mode::ab,   mode::rw,   mode::ab   }, 0 },
+	{ "SCANC"sv,  { mode::rw,   mode::ab,   mode::ab,   mode::urb,  mode::none, mode::none }, 0 },
+	{ "SPANC"sv,  { mode::rw,   mode::ab,   mode::ab,   mode::urb,  mode::none, mode::none }, 0 },
+	{ "MOVC5"sv,  { mode::rw,   mode::ab,   mode::urb,  mode::rw,   mode::ab,   mode::none }, 0 },
+	{ "CMPC5"sv,  { mode::rw,   mode::ab,   mode::urb,  mode::rw,   mode::ab,   mode::none }, 0 },
+	{ "MOVTC"sv,  { mode::rw,   mode::ab,   mode::urb,  mode::ab,   mode::rw,   mode::ab   }, 0 },
+	{ "MOVTUC"sv, { mode::rw,   mode::ab,   mode::urb,  mode::ab,   mode::rw,   mode::ab   }, 0 },
 
 	{ "BSBW"sv,   { mode::bw,   mode::none, mode::none, mode::none, mode::none, mode::none }, vax_disassembler::STEP_OVER },
 	{ "BRW"sv,    { mode::bw,   mode::none, mode::none, mode::none, mode::none, mode::none }, 0 },
@@ -397,8 +397,8 @@ static const vax_disassembler::opdef s_nonprefix_ops[0x100 - 3] =
 	{ "CMPP4"sv,  { mode::rw,   mode::ab,   mode::rw,   mode::ab,   mode::none, mode::none }, 0 },
 	{ "EDITPC"sv, { mode::rw,   mode::ab,   mode::ab,   mode::ab,   mode::none, mode::none }, 0 },
 	{ "MATCHC"sv, { mode::rw,   mode::ab,   mode::rw,   mode::ab,   mode::none, mode::none }, 0 },
-	{ "LOCC"sv,   { mode::rb,   mode::rw,   mode::ab,   mode::none, mode::none, mode::none }, 0 },
-	{ "SKPC"sv,   { mode::rb,   mode::rw,   mode::ab,   mode::none, mode::none, mode::none }, 0 },
+	{ "LOCC"sv,   { mode::urb,  mode::rw,   mode::ab,   mode::none, mode::none, mode::none }, 0 },
+	{ "SKPC"sv,   { mode::urb,  mode::rw,   mode::ab,   mode::none, mode::none, mode::none }, 0 },
 	{ "MOVZWL"sv, { mode::rw,   mode::wl,   mode::none, mode::none, mode::none, mode::none }, 0 },
 	{ "ACBW"sv,   { mode::srw,  mode::srw,  mode::mw,   mode::bw,   mode::none, mode::none }, vax_disassembler::STEP_COND },
 	{ "MOVAW"sv,  { mode::aw,   mode::wl,   mode::none, mode::none, mode::none, mode::none }, 0 },
@@ -954,6 +954,7 @@ offs_t vax_disassembler::disassemble_inst(std::ostream &stream, const vax_disass
 					else switch (inst.operand[n])
 					{
 					case mode::rb:
+					case mode::ab: // Immediate bytes may be used as MOVCn sources, at least with a length of 0
 						format_immediate(stream, opcodes.r8(pc++));
 						break;
 
@@ -963,7 +964,6 @@ offs_t vax_disassembler::disassemble_inst(std::ostream &stream, const vax_disass
 						break;
 
 					case mode::urb:
-					case mode::ab: // Immediate bytes may be used as MOVCn sources
 						util::stream_format(stream, "#^X%02X", opcodes.r8(pc++));
 						break;