diff --git a/py/modbuiltins.c b/py/modbuiltins.c
index ebff5f5c0c..0c78832aca 100644
--- a/py/modbuiltins.c
+++ b/py/modbuiltins.c
@@ -457,16 +457,14 @@ STATIC mp_obj_t mp_builtin_round(size_t n_args, const mp_obj_t *args) {
         return o_in;
     }
 #if MICROPY_PY_BUILTINS_FLOAT
-    mp_int_t num_dig = 0;
+    mp_float_t val = mp_obj_get_float(o_in);
     if (n_args > 1) {
-        num_dig = mp_obj_get_int(args[1]);
-        mp_float_t val = mp_obj_get_float(o_in);
+        mp_int_t num_dig = mp_obj_get_int(args[1]);
         mp_float_t mult = MICROPY_FLOAT_C_FUN(pow)(10, num_dig);
         // TODO may lead to overflow
         mp_float_t rounded = MICROPY_FLOAT_C_FUN(nearbyint)(val * mult) / mult;
         return mp_obj_new_float(rounded);
     }
-    mp_float_t val = mp_obj_get_float(o_in);
     mp_float_t rounded = MICROPY_FLOAT_C_FUN(nearbyint)(val);
     return mp_obj_new_int_from_float(rounded);
 #else