diff --git a/Assets/Plugins/UniRx/Scripts/UnityEngineBridge/ReactiveDictionary.cs b/Assets/Plugins/UniRx/Scripts/UnityEngineBridge/ReactiveDictionary.cs
index 4b928e30d..4b0f5bc10 100644
--- a/Assets/Plugins/UniRx/Scripts/UnityEngineBridge/ReactiveDictionary.cs
+++ b/Assets/Plugins/UniRx/Scripts/UnityEngineBridge/ReactiveDictionary.cs
@@ -123,6 +123,11 @@ public class ReactiveDictionary<TKey, TValue> : IReactiveDictionary<TKey, TValue
         [UnityEngine.SerializeField]
 #endif
         readonly Dictionary<TKey, TValue> inner;
+        
+        public bool IsNull()
+        {
+            return inner == null;
+        }
 
         public ReactiveDictionary()
         {