diff --git a/core/object.rbs b/core/object.rbs
index 6669731..bbbc532 100644
--- a/core/object.rbs
+++ b/core/object.rbs
@@ -84,4 +84,8 @@ class Object < BasicObject
   alias self.inspect self.to_s
 
   def loop: () { () -> void } -> bot
+
+  def sleep: (Integer | Float sec) -> Integer
+
+  def sleep_ms: (Integer ms) -> Integer
 end
diff --git a/test/object.rb b/test/object.rb
index a996552..8f23048 100644
--- a/test/object.rb
+++ b/test/object.rb
@@ -128,4 +128,9 @@ module TestMod end
 
 loop { puts }
 
+sleep 1
+sleep 1.0
+
+sleep_ms 1000
+
 # rubocop:enable all