diff --git a/src/vm.c b/src/vm.c
index 99b87d9ce..4f5657e2a 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -1187,8 +1187,6 @@ catch_handler_find(const mrb_irep *irep, const mrb_code *pc, uint32_t filter)
 static void
 argnum_error(mrb_state *mrb, mrb_int num)
 {
-  mrb_value exc;
-  mrb_value str;
   mrb_int argc = mrb->c->ci->n;
 
   if (argc == 15) {
@@ -1200,8 +1198,8 @@ argnum_error(mrb_state *mrb, mrb_int num)
   if (argc == 0 && mrb->c->ci->nk != 0 && !mrb_hash_empty_p(mrb, mrb->c->ci->stack[1])) {
     argc++;
   }
-  str = mrb_format(mrb, "wrong number of arguments (given %i, expected %i)", argc, num);
-  exc = mrb_exc_new_str(mrb, E_ARGUMENT_ERROR, str);
+  mrb_value str = mrb_format(mrb, "wrong number of arguments (given %i, expected %i)", argc, num);
+  mrb_value exc = mrb_exc_new_str(mrb, E_ARGUMENT_ERROR, str);
   mrb_exc_set(mrb, exc);
 }