diff --git a/scheduler.c b/scheduler.c
index 03caec8d6f..d7e713a710 100644
--- a/scheduler.c
+++ b/scheduler.c
@@ -43,6 +43,8 @@ rb_scheduler_close(VALUE scheduler)
     if (rb_respond_to(scheduler, id_close)) {
         return rb_funcall(scheduler, id_close, 0);
     }
+
+    return Qnil;
 }
 
 VALUE