diff --git a/py/bc.c b/py/bc.c
index 89d8b74f91..1d6e4322b2 100644
--- a/py/bc.c
+++ b/py/bc.c
@@ -292,7 +292,7 @@ continue2:;
 //     MP_BC_MAKE_CLOSURE_DEFARGS
 //     MP_BC_RAISE_VARARGS
 // There are 4 special opcodes that have an extra byte only when
-// MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE is enabled:
+// MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE is enabled (and they take a qstr):
 //     MP_BC_LOAD_NAME
 //     MP_BC_LOAD_GLOBAL
 //     MP_BC_LOAD_ATTR
@@ -386,18 +386,20 @@ uint mp_opcode_format(const byte *ip, size_t *opcode_size) {
     uint f = (opcode_format_table[*ip >> 2] >> (2 * (*ip & 3))) & 3;
     const byte *ip_start = ip;
     if (f == MP_OPCODE_QSTR) {
+        if (MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE_DYNAMIC) {
+            if (*ip == MP_BC_LOAD_NAME
+                || *ip == MP_BC_LOAD_GLOBAL
+                || *ip == MP_BC_LOAD_ATTR
+                || *ip == MP_BC_STORE_ATTR) {
+                ip += 1;
+            }
+        }
         ip += 3;
     } else {
         int extra_byte = (
             *ip == MP_BC_RAISE_VARARGS
             || *ip == MP_BC_MAKE_CLOSURE
             || *ip == MP_BC_MAKE_CLOSURE_DEFARGS
-            #if MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE
-            || *ip == MP_BC_LOAD_NAME
-            || *ip == MP_BC_LOAD_GLOBAL
-            || *ip == MP_BC_LOAD_ATTR
-            || *ip == MP_BC_STORE_ATTR
-            #endif
         );
         ip += 1;
         if (f == MP_OPCODE_VAR_UINT) {