diff --git a/com.unity.netcode.gameobjects/Runtime/Core/NetworkManager.cs b/com.unity.netcode.gameobjects/Runtime/Core/NetworkManager.cs
index c0633da1f4..b793214078 100644
--- a/com.unity.netcode.gameobjects/Runtime/Core/NetworkManager.cs
+++ b/com.unity.netcode.gameobjects/Runtime/Core/NetworkManager.cs
@@ -1134,6 +1134,8 @@ public int MaximumFragmentedMessageSize
 
         internal void Initialize(bool server)
         {
+            UnityEngine.Assertions.Assert.IsNotNull(Singleton);
+
 #if DEVELOPMENT_BUILD || UNITY_EDITOR
             if (!DisableNotOptimizedSerializedType)
             {