diff --git a/py/modbuiltins.c b/py/modbuiltins.c
index c169b2ee4..c4de325c1 100644
--- a/py/modbuiltins.c
+++ b/py/modbuiltins.c
@@ -217,7 +217,12 @@ STATIC mp_obj_t mp_builtin_hash(mp_obj_t o_in) {
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_hash_obj, mp_builtin_hash);
 
 STATIC mp_obj_t mp_builtin_hex(mp_obj_t o_in) {
+    #if MICROPY_PY_BUILTINS_STR_OP_MODULO
     return mp_binary_op(MP_BINARY_OP_MODULO, MP_OBJ_NEW_QSTR(MP_QSTR__percent__hash_x), o_in);
+    #else
+    mp_obj_t args[] = { MP_OBJ_NEW_QSTR(MP_QSTR__brace_open__colon__hash_x_brace_close_), o_in };
+    return mp_obj_str_format(MP_ARRAY_SIZE(args), args, NULL);
+    #endif
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_hex_obj, mp_builtin_hex);
 
@@ -322,7 +327,12 @@ STATIC mp_obj_t mp_builtin_next(mp_obj_t o) {
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_next_obj, mp_builtin_next);
 
 STATIC mp_obj_t mp_builtin_oct(mp_obj_t o_in) {
+    #if MICROPY_PY_BUILTINS_STR_OP_MODULO
     return mp_binary_op(MP_BINARY_OP_MODULO, MP_OBJ_NEW_QSTR(MP_QSTR__percent__hash_o), o_in);
+    #else
+    mp_obj_t args[] = { MP_OBJ_NEW_QSTR(MP_QSTR__brace_open__colon__hash_o_brace_close_), o_in };
+    return mp_obj_str_format(MP_ARRAY_SIZE(args), args, NULL);
+    #endif
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_oct_obj, mp_builtin_oct);
 
diff --git a/py/qstrdefs.h b/py/qstrdefs.h
index a60905812..5c8b13b47 100644
--- a/py/qstrdefs.h
+++ b/py/qstrdefs.h
@@ -37,8 +37,13 @@ Q()
 Q(*)
 Q(_)
 Q(/)
+#if MICROPY_PY_BUILTINS_STR_OP_MODULO
 Q(%#o)
 Q(%#x)
+#else
+Q({:#o})
+Q({:#x})
+#endif
 Q({:#b})
 Q( )
 Q(\n)