diff --git a/src/ca65/instr.c b/src/ca65/instr.c
index 745072a09..2ed5ba734 100644
--- a/src/ca65/instr.c
+++ b/src/ca65/instr.c
@@ -181,7 +181,7 @@ static const struct {
         { "BMI",  0x0020000, 0x30, 0, PutPCRel8 },
         { "BNE",  0x0020000, 0xd0, 0, PutPCRel8 },
         { "BPL",  0x0020000, 0x10, 0, PutPCRel8 },
-        { "BRK",  0x0000001, 0x00, 0, PutAll },
+        { "BRK",  0x0000005, 0x00, 6, PutAll },
         { "BVC",  0x0020000, 0x50, 0, PutPCRel8 },
         { "BVS",  0x0020000, 0x70, 0, PutPCRel8 },
         { "CLC",  0x0000001, 0x18, 0, PutAll },
@@ -252,7 +252,7 @@ static const struct {
         { "BMI",  0x0020000, 0x30, 0, PutPCRel8 },
         { "BNE",  0x0020000, 0xd0, 0, PutPCRel8 },
         { "BPL",  0x0020000, 0x10, 0, PutPCRel8 },
-        { "BRK",  0x0000001, 0x00, 0, PutAll },
+        { "BRK",  0x0000005, 0x00, 6, PutAll },
         { "BVC",  0x0020000, 0x50, 0, PutPCRel8 },
         { "BVS",  0x0020000, 0x70, 0, PutPCRel8 },
         { "CLC",  0x0000001, 0x18, 0, PutAll },
@@ -342,7 +342,7 @@ static const struct {
         { "BNE",  0x0020000, 0xd0, 0, PutPCRel8 },
         { "BPL",  0x0020000, 0x10, 0, PutPCRel8 },
         { "BRA",  0x0020000, 0x12, 0, PutPCRel8 },      /* DTV */
-        { "BRK",  0x0000001, 0x00, 0, PutAll },
+        { "BRK",  0x0000005, 0x00, 6, PutAll },
         { "BVC",  0x0020000, 0x50, 0, PutPCRel8 },
         { "BVS",  0x0020000, 0x70, 0, PutPCRel8 },
         { "CLC",  0x0000001, 0x18, 0, PutAll },
@@ -418,7 +418,7 @@ static const struct {
         { "BNE",  0x0020000, 0xd0, 0, PutPCRel8 },
         { "BPL",  0x0020000, 0x10, 0, PutPCRel8 },
         { "BRA",  0x0020000, 0x80, 0, PutPCRel8 },
-        { "BRK",  0x0000001, 0x00, 0, PutAll },
+        { "BRK",  0x0000005, 0x00, 6, PutAll },
         { "BVC",  0x0020000, 0x50, 0, PutPCRel8 },
         { "BVS",  0x0020000, 0x70, 0, PutPCRel8 },
         { "CLC",  0x0000001, 0x18, 0, PutAll },
@@ -510,7 +510,7 @@ static const struct {
         { "BNE",  0x0020000, 0xd0, 0, PutPCRel8 },
         { "BPL",  0x0020000, 0x10, 0, PutPCRel8 },
         { "BRA",  0x0020000, 0x80, 0, PutPCRel8 },
-        { "BRK",  0x0000001, 0x00, 0, PutAll },
+        { "BRK",  0x0000005, 0x00, 6, PutAll },
         { "BVC",  0x0020000, 0x50, 0, PutPCRel8 },
         { "BVS",  0x0020000, 0x70, 0, PutPCRel8 },
         { "CLC",  0x0000001, 0x18, 0, PutAll },
@@ -622,7 +622,7 @@ static const struct {
         { "BNE",  0x0020000, 0xd0, 0, PutPCRel8 },
         { "BPL",  0x0020000, 0x10, 0, PutPCRel8 },
         { "BRA",  0x0020000, 0x80, 0, PutPCRel8 },
-        { "BRK",  0x0000001, 0x00, 0, PutAll },
+        { "BRK",  0x0000005, 0x00, 6, PutAll },
         { "BSR",  0x0040000, 0x63, 0, PutPCRel4510 },
         { "BVC",  0x0020000, 0x50, 0, PutPCRel8 },
         { "BVS",  0x0020000, 0x70, 0, PutPCRel8 },
@@ -756,7 +756,7 @@ static const struct {
         { "CLI",  0x0000001, 0x58, 0, PutAll },
         { "CLV",  0x0000001, 0xb8, 0, PutAll },
         { "CMP",  0x0b8f6fc, 0xc0, 0, PutAll },
-        { "COP",  0x0000004, 0x02, 6, PutAll },
+        { "COP",  0x0000005, 0x02, 6, PutAll },
         { "CPA",  0x0b8f6fc, 0xc0, 0, PutAll },   /* == CMP */
         { "CPX",  0x0c0000c, 0xe0, 1, PutAll },
         { "CPY",  0x0c0000c, 0xc0, 1, PutAll },
@@ -909,7 +909,7 @@ static const struct {
         { "BNE",  0x0020000, 0xd0, 0, PutPCRel8 },
         { "BPL",  0x0020000, 0x10, 0, PutPCRel8 },
         { "BRA",  0x0020000, 0x80, 0, PutPCRel8 },
-        { "BRK",  0x0000001, 0x00, 0, PutAll },
+        { "BRK",  0x0000005, 0x00, 6, PutAll },
         { "BSR",  0x0020000, 0x44, 0, PutPCRel8 },
         { "BVC",  0x0020000, 0x50, 0, PutPCRel8 },
         { "BVS",  0x0020000, 0x70, 0, PutPCRel8 },
diff --git a/test/asm/listing/109-brk-signature.s b/test/asm/listing/109-brk-signature.s
new file mode 100644
index 000000000..b150e088a
--- /dev/null
+++ b/test/asm/listing/109-brk-signature.s
@@ -0,0 +1,36 @@
+; test of optional signature byte for BRK on all 6502-derived CPUs
+; and also COP on 65C816
+
+.setcpu "6502"
+brk ; 1 byte
+brk 0 ; 2 bytes
+brk $60 ; 2 bytes
+
+.setcpu "6502X"
+brk
+brk $60
+
+.setcpu "6502DTV"
+brk
+brk $60
+
+.setcpu "65SC02"
+brk
+brk $60
+
+.setcpu "65816"
+brk
+brk $60
+cop
+cop $60
+; WDM is a NOP that gives +2 PC, probably not useful to make its signature byte optional
+;wdm
+wdm $60
+
+.setcpu "4510"
+brk
+brk $60
+
+.setcpu "HuC6280"
+brk
+brk $60
diff --git a/test/asm/listing/ref/109-brk-signature.bin-ref b/test/asm/listing/ref/109-brk-signature.bin-ref
new file mode 100644
index 000000000..0f46d29fd
Binary files /dev/null and b/test/asm/listing/ref/109-brk-signature.bin-ref differ