diff --git a/src/common/cpu.c b/src/common/cpu.c
index 2c29eb1c4..54bb8a3fb 100644
--- a/src/common/cpu.c
+++ b/src/common/cpu.c
@@ -66,20 +66,26 @@ const char* CPUNames[CPU_COUNT] = {
     "45GS02"
 };
 
-/* Tables with CPU instruction sets */
+/* Tables with CPU instruction sets
+ * NOTE: make sure to only combine the instruction sets that are 100% compatible
+ */
 const unsigned CPUIsets[CPU_COUNT] = {
     CPU_ISET_NONE,
     CPU_ISET_6502,
-    CPU_ISET_6502 | CPU_ISET_6502X,
-    CPU_ISET_6502 | CPU_ISET_6502DTV,
-    CPU_ISET_6502 | CPU_ISET_65SC02,
-    CPU_ISET_6502 | CPU_ISET_65SC02 | CPU_ISET_65C02,
-    CPU_ISET_6502 | CPU_ISET_65SC02 | CPU_ISET_65C02 | CPU_ISET_65816,
+    CPU_ISET_6502X   | CPU_ISET_6502,
+    CPU_ISET_6502DTV | CPU_ISET_6502,
+    CPU_ISET_65SC02  | CPU_ISET_6502,
+    CPU_ISET_65C02   | CPU_ISET_6502 | CPU_ISET_65SC02,
+    /* FIXME: does 65816 have both wai/stp and indirect-zp (without z)? */
+    CPU_ISET_65816   | CPU_ISET_6502 | CPU_ISET_65SC02 | CPU_ISET_65C02,
     CPU_ISET_SWEET16,
-    CPU_ISET_6502 | CPU_ISET_65SC02 | CPU_ISET_65C02 | CPU_ISET_HUC6280,
-    CPU_ISET_6502 | CPU_ISET_M740,
-    CPU_ISET_6502 | CPU_ISET_65SC02 | CPU_ISET_65C02 | CPU_ISET_4510,
-    CPU_ISET_6502 | CPU_ISET_65SC02 | CPU_ISET_65C02 | CPU_ISET_4510 | CPU_ISET_45GS02,
+    /* FIXME: HUC6280 does not have wai/stp */
+    CPU_ISET_HUC6280 | CPU_ISET_6502 | CPU_ISET_65SC02 | CPU_ISET_65C02,
+    CPU_ISET_M740    | CPU_ISET_6502,
+    /* 4510 does NOT have indirect-zp (without z), so we can not use 65SC02 */
+    /* FIXME: 4510 does not have wai/stp */
+    CPU_ISET_4510    | CPU_ISET_6502 |  CPU_ISET_65C02,
+    CPU_ISET_45GS02  | CPU_ISET_6502 |  CPU_ISET_65C02 | CPU_ISET_4510,
 };
 
 
diff --git a/src/common/cpu.h b/src/common/cpu.h
index 6d8b72469..81795e146 100644
--- a/src/common/cpu.h
+++ b/src/common/cpu.h
@@ -47,7 +47,7 @@
 /* CPUs */
 typedef enum {
     CPU_UNKNOWN = -1,           /* Not specified or invalid target */
-    CPU_NONE,                   /* No CPU - for assembler */
+    CPU_NONE = 0,               /* No CPU - for assembler */
     CPU_6502,
     CPU_6502X,                  /* "Extended", that is: with illegal opcodes */
     CPU_6502DTV,                /* CPU_6502 + DTV extra and illegal opcodes */
@@ -62,7 +62,7 @@ typedef enum {
     CPU_COUNT                   /* Number of different CPUs */
 } cpu_t;
 
-/* CPU instruction sets */
+/* CPU instruction sets (make sure this matches asminc/cpu.mac) */
 enum {
     CPU_ISET_NONE       = 1 << CPU_NONE,
     CPU_ISET_6502       = 1 << CPU_6502,