diff --git a/include/mruby.h b/include/mruby.h
index be52e962b..3960a9e35 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -324,7 +324,7 @@ void mrb_bug(const char *fmt, ...);
 
 #define E_KEY_ERROR                 (mrb_class_get(mrb, "KeyError"))
 
-mrb_value mrb_yield(mrb_state *mrb, mrb_value v, mrb_value blk);
+mrb_value mrb_yield(mrb_state *mrb, mrb_value b, mrb_value arg);
 mrb_value mrb_yield_argv(mrb_state *mrb, mrb_value b, int argc, mrb_value *argv);
 mrb_value mrb_class_new_instance(mrb_state *mrb, int, mrb_value*, struct RClass *);
 mrb_value mrb_class_new_instance_m(mrb_state *mrb, mrb_value klass);
diff --git a/src/vm.c b/src/vm.c
index 4b2198195..4794323c7 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -449,11 +449,11 @@ mrb_yield_argv(mrb_state *mrb, mrb_value b, int argc, mrb_value *argv)
 }
 
 mrb_value
-mrb_yield(mrb_state *mrb, mrb_value b, mrb_value v)
+mrb_yield(mrb_state *mrb, mrb_value b, mrb_value arg)
 {
   struct RProc *p = mrb_proc_ptr(b);
 
-  return mrb_yield_internal(mrb, b, 1, &v, mrb->stack[0], p->target_class);
+  return mrb_yield_internal(mrb, b, 1, &arg, mrb->stack[0], p->target_class);
 }
 
 typedef enum {