diff --git a/src/Components/Server/src/Microsoft.AspNetCore.Components.Server.csproj b/src/Components/Server/src/Microsoft.AspNetCore.Components.Server.csproj
index 2e66dffc7e..04475e3540 100644
--- a/src/Components/Server/src/Microsoft.AspNetCore.Components.Server.csproj
+++ b/src/Components/Server/src/Microsoft.AspNetCore.Components.Server.csproj
@@ -8,7 +8,7 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <NoWarn>CS0436;$(NoWarn)</NoWarn>
-    <DefineConstants>$(DefineConstants);MESSAGEPACK_INTERNAL;COMPONENTS_SERVER</DefineConstants>
+    <DefineConstants>$(DefineConstants);ENABLE_UNSAFE_MSGPACK;SPAN_BUILTIN;MESSAGEPACK_INTERNAL;COMPONENTS_SERVER</DefineConstants>
     <IsShippingPackage>false</IsShippingPackage>
   </PropertyGroup>
 
@@ -36,7 +36,7 @@
   </ItemGroup>
 
   <PropertyGroup>
-    <MessagePackRoot>$(RepoRoot)src\submodules\MessagePack-CSharp\src\MessagePack\</MessagePackRoot>
+    <MessagePackRoot>$(RepoRoot)src\submodules\MessagePack-CSharp\src\MessagePack.UnityClient\Assets\Scripts\MessagePack\</MessagePackRoot>
   </PropertyGroup>
 
   <ItemGroup>
@@ -58,15 +58,16 @@
     <Compile Include="$(MessagePackRoot)ExtensionResult.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)MessagePackCode.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)MessagePackReader.cs" LinkBase="BlazorPack\MessagePack" />
-    <Compile Include="$(MessagePackRoot)MessagePackReader.Integers.cs" LinkBase="BlazorPack\MessagePack" />
+    <Compile Include="$(MessagePackRoot)T4\MessagePackReader.Integers.cs" LinkBase="BlazorPack\MessagePack" />
+    <Compile Include="$(MessagePackRoot)MessagePackSerializationException.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)MessagePackWriter.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)Nil.cs" LinkBase="BlazorPack\MessagePack" />
-    <Compile Include="$(MessagePackRoot)FloatBits.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)Internal\DateTimeConstants.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)StringEncoding.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)SequencePool.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)SequenceReader.cs" LinkBase="BlazorPack\MessagePack" />
     <Compile Include="$(MessagePackRoot)SequenceReaderExtensions.cs" LinkBase="BlazorPack\MessagePack" />
+    <Compile Include="$(MessagePackRoot)Utilities.cs" LinkBase="BlazorPack\MessagePack" />
 
     <!-- Shared descriptor infrastructure with MVC -->
     <Compile Include="$(RepoRoot)src\Shared\Components\ServerComponent.cs" />
@@ -84,4 +85,4 @@
     <EmbeddedResource Include="$(BlazorServerJSFile).map" LogicalName="_framework/%(Filename)%(Extension)" Condition="Exists('$(BlazorServerJSFile).map')" />
   </ItemGroup>
 
-</Project>
+</Project>
\ No newline at end of file
diff --git a/src/submodules/MessagePack-CSharp b/src/submodules/MessagePack-CSharp
index 8861abdde9..a4a14ce447 160000
--- a/src/submodules/MessagePack-CSharp
+++ b/src/submodules/MessagePack-CSharp
@@ -1 +1 @@
-Subproject commit 8861abdde93a3b97180ac3b2eafa33459ad52392
+Subproject commit a4a14ce447e4ef694af1a485fb672db35e766111