diff --git a/Assets/Mirror/Core/Messages.cs b/Assets/Mirror/Core/Messages.cs
index 62888c07e6..15cadde894 100644
--- a/Assets/Mirror/Core/Messages.cs
+++ b/Assets/Mirror/Core/Messages.cs
@@ -52,13 +52,14 @@ public struct RpcMessage : NetworkMessage
         public ArraySegment<byte> payload;
     }
 
+    [Flags] public enum AuthorityFlags : byte { None, isOwner, isLocalPlayer }
+
     public struct SpawnMessage : NetworkMessage
     {
         // netId of new or existing object
         public uint netId;
-        public bool isLocalPlayer;
-        // Sets hasAuthority on the spawned object
-        public bool isOwner;
+        // isOwner and isLocalPlayer are merged into one byte via bitwise op
+        public AuthorityFlags authorityFlags;
         public ulong sceneId;
         // If sceneId != 0 then it is used instead of assetId
         public uint assetId;
@@ -71,13 +72,53 @@ public struct SpawnMessage : NetworkMessage
         // serialized component data
         // ArraySegment to avoid unnecessary allocations
         public ArraySegment<byte> payload;
+
+        // Backwards compatibility after implementing authorityFlags
+        public bool isOwner
+        {
+            get => authorityFlags.HasFlag(AuthorityFlags.isOwner);
+            set => authorityFlags = 
+                value 
+                ? authorityFlags | AuthorityFlags.isOwner 
+                : authorityFlags & ~AuthorityFlags.isOwner;
+        }
+
+        // Backwards compatibility after implementing authorityFlags
+        public bool isLocalPlayer
+        {
+            get => authorityFlags.HasFlag(AuthorityFlags.isLocalPlayer);
+            set => authorityFlags = 
+                value 
+                ? authorityFlags | AuthorityFlags.isLocalPlayer 
+                : authorityFlags & ~AuthorityFlags.isLocalPlayer;
+        }
     }
 
     public struct ChangeOwnerMessage : NetworkMessage
     {
         public uint netId;
-        public bool isOwner;
-        public bool isLocalPlayer;
+        // isOwner and isLocalPlayer are merged into one byte via bitwise op
+        public AuthorityFlags authorityFlags;
+
+        // Backwards compatibility after implementing authorityFlags
+        public bool isOwner
+        {
+            get => authorityFlags.HasFlag(AuthorityFlags.isOwner);
+            set => authorityFlags = 
+                value 
+                ? authorityFlags | AuthorityFlags.isOwner 
+                : authorityFlags & ~AuthorityFlags.isOwner;
+        }
+
+        // Backwards compatibility after implementing authorityFlags
+        public bool isLocalPlayer
+        {
+            get => authorityFlags.HasFlag(AuthorityFlags.isLocalPlayer);
+            set => authorityFlags = 
+                value 
+                ? authorityFlags | AuthorityFlags.isLocalPlayer 
+                : authorityFlags & ~AuthorityFlags.isLocalPlayer;
+        }
     }
 
     public struct ObjectSpawnStartedMessage : NetworkMessage {}