diff --git a/src/AwsLambdaTestServer/MartinCostello.Testing.AwsLambdaTestServer.csproj b/src/AwsLambdaTestServer/MartinCostello.Testing.AwsLambdaTestServer.csproj
index 1383966b..c071a13d 100644
--- a/src/AwsLambdaTestServer/MartinCostello.Testing.AwsLambdaTestServer.csproj
+++ b/src/AwsLambdaTestServer/MartinCostello.Testing.AwsLambdaTestServer.csproj
@@ -24,7 +24,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.TestHost" />
     <PackageReference Update="Microsoft.AspNetCore.TestHost" VersionOverride="8.0.0" Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))" />
-    <PackageReference Update="Microsoft.AspNetCore.TestHost" VersionOverride="9.0.0-preview.3.24172.13" Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net9.0'))" />
+    <PackageReference Update="Microsoft.AspNetCore.TestHost" VersionOverride="9.0.0-preview.4.24267.6" Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net9.0'))" />
   </ItemGroup>
   <ItemGroup>
     <AdditionalFiles Include="PublicAPI\PublicAPI.Shipped.txt" />