diff --git a/.github/workflows/release-nuget.yaml b/.github/workflows/release-nuget.yaml
index 930311202..46aade6da 100644
--- a/.github/workflows/release-nuget.yaml
+++ b/.github/workflows/release-nuget.yaml
@@ -15,7 +15,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: 8.0.x
+          dotnet-version: 9.0.x
       - uses: cucumber/action-publish-nuget@v1.0.0
         with:
           nuget-api-key: ${{ secrets.NUGET_API_KEY }}
diff --git a/.github/workflows/test-dotnet.yml b/.github/workflows/test-dotnet.yml
index 421fbc914..884235112 100644
--- a/.github/workflows/test-dotnet.yml
+++ b/.github/workflows/test-dotnet.yml
@@ -27,6 +27,7 @@ jobs:
         with:
           dotnet-version: |
             8.0.x
+            9.0.x
       - run: dotnet test
         working-directory: dotnet
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2ad35a5a..858845f35 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ This document is formatted according to the principles of [Keep A CHANGELOG](htt
 - [PHP, Java, Ruby, JavaScript] update dependency messages up to v26
 - [Python] Added type annotations ([#283](https://github.com/cucumber/gherkin/pull/283))
 - [Python] Switch to pyproject.toml ([#290](https://github.com/cucumber/gherkin/pull/290))
+- [.NET] Added .NET 9 to test matrix
 
 ### Changed
 - [.NET] Drop unsupported frameworks. Now supported target frameworks are .NET 8, .NET Standard 2.0 ([#265](https://github.com/cucumber/gherkin/pull/265))
diff --git a/dotnet/Directory.Build.props b/dotnet/Directory.Build.props
index e454fc19b..80110d548 100644
--- a/dotnet/Directory.Build.props
+++ b/dotnet/Directory.Build.props
@@ -1,7 +1,7 @@
 <Project>
 
   <PropertyGroup>
-    <LangVersion>12</LangVersion>
+    <LangVersion>13</LangVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
diff --git a/dotnet/Gherkin.Specs/DependencyValidationTests.cs b/dotnet/Gherkin.Specs/DependencyValidationTests.cs
index 06d932b53..2600daab1 100644
--- a/dotnet/Gherkin.Specs/DependencyValidationTests.cs
+++ b/dotnet/Gherkin.Specs/DependencyValidationTests.cs
@@ -15,7 +15,7 @@ public void SystemTextJsonUpgradeBlocker()
 
         var version = typeof(JsonSerializer).Assembly.GetCustomAttribute<AssemblyFileVersionAttribute>().Version;
 
-        Assert.Equal("6.0.3524.45918", version); // System.Text.Json Version 6.0.10
+        Assert.Equal("8.0.1024.46610", version); // System.Text.Json Version 8.0.5
     }
 }
 #endif
\ No newline at end of file
diff --git a/dotnet/Gherkin.Specs/Gherkin.Specs.csproj b/dotnet/Gherkin.Specs/Gherkin.Specs.csproj
index 3343a1056..6c3b649d0 100644
--- a/dotnet/Gherkin.Specs/Gherkin.Specs.csproj
+++ b/dotnet/Gherkin.Specs/Gherkin.Specs.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   
   <PropertyGroup>
-    <TargetFrameworks>net8.0;net462</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;net462</TargetFrameworks>
     <OutputType>Exe</OutputType>
     <StartupObject>Gherkin.Specs.CLI.Program</StartupObject>
   </PropertyGroup>
diff --git a/dotnet/Gherkin/Gherkin.csproj b/dotnet/Gherkin/Gherkin.csproj
index e5f1152fa..b2aefc0aa 100644
--- a/dotnet/Gherkin/Gherkin.csproj
+++ b/dotnet/Gherkin/Gherkin.csproj
@@ -33,7 +33,7 @@
   </PropertyGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
-    <PackageReference Include="System.Text.Json" Version="6.0.10"/>
+    <PackageReference Include="System.Text.Json" Version="8.0.5" />
   </ItemGroup>
 
   <ItemGroup>