diff --git a/build/Base.props b/build/Base.props
index 22107d2..10d667d 100644
--- a/build/Base.props
+++ b/build/Base.props
@@ -1,6 +1,6 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
-    <VersionPrefix>0.8.2.1</VersionPrefix>
+    <VersionPrefix>0.9.0</VersionPrefix>
     <VersionSuffix></VersionSuffix>
     <Authors>Wiesław Šoltés</Authors>
     <Company>Wiesław Šoltés</Company>
@@ -8,4 +8,7 @@
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/wieslawsoltes/SimpleWavSplitter</PackageProjectUrl>
   </PropertyGroup>
+  <PropertyGroup>
+    <LangVersion>8.0</LangVersion>
+  </PropertyGroup>
 </Project>
diff --git a/src/SimpleWavSplitter.Avalonia/MainWindow.xaml.cs b/src/SimpleWavSplitter.Avalonia/MainWindow.xaml.cs
index 5e73bbc..b56c3df 100644
--- a/src/SimpleWavSplitter.Avalonia/MainWindow.xaml.cs
+++ b/src/SimpleWavSplitter.Avalonia/MainWindow.xaml.cs
@@ -42,7 +42,7 @@ namespace SimpleWavSplitter.Avalonia
             textOutput = this.FindControl<TextBox>("textOutput");
 
             var version = Assembly.GetExecutingAssembly().GetName().Version;
-            Title = string.Format("SimpleWavSplitter v{0}.{1}.{2}", version.Major, version.Minor, version.Build);
+            Title = string.Format("SimpleWavSplitter v{0}.{1}.{2}", version?.Major, version?.Minor, version?.Build);
 
             btnBrowseOutputPath.Click += async (sender, e) => await GetOutputPath();
             btnGetWavHeader.Click += async (sender, e) => await GetWavHeader();
diff --git a/src/SimpleWavSplitter.Avalonia/SimpleWavSplitter.Avalonia.csproj b/src/SimpleWavSplitter.Avalonia/SimpleWavSplitter.Avalonia.csproj
index d2cffc3..abd113b 100644
--- a/src/SimpleWavSplitter.Avalonia/SimpleWavSplitter.Avalonia.csproj
+++ b/src/SimpleWavSplitter.Avalonia/SimpleWavSplitter.Avalonia.csproj
@@ -5,8 +5,8 @@
     <OutputType>WinExe</OutputType>
     <GeneratePackageOnBuild>False</GeneratePackageOnBuild>
     <EnableDefaultCompileItems>False</EnableDefaultCompileItems>
-    <LangVersion>latest</LangVersion>
     <IsPackable>False</IsPackable>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/src/SimpleWavSplitter.Console/Program.cs b/src/SimpleWavSplitter.Console/Program.cs
index 0d26336..4fcfa63 100644
--- a/src/SimpleWavSplitter.Console/Program.cs
+++ b/src/SimpleWavSplitter.Console/Program.cs
@@ -37,7 +37,7 @@ namespace SimpleWavSplitter.Console
                 WriteLine(
                     string.Format(
                         "SimpleWavSplitterConsole v{0}.{1}.{2}",
-                        v.Major, v.Minor, v.Build));
+                        v?.Major, v?.Minor, v?.Build));
                 Write(Environment.NewLine);
                 WriteLine("Usage:");
                 WriteLine("SimpleWavSplitter.Console <file.wav> [<OutputPath>]");
diff --git a/src/SimpleWavSplitter.Console/SimpleWavSplitter.Console.csproj b/src/SimpleWavSplitter.Console/SimpleWavSplitter.Console.csproj
index 5cdabb5..ad297bf 100644
--- a/src/SimpleWavSplitter.Console/SimpleWavSplitter.Console.csproj
+++ b/src/SimpleWavSplitter.Console/SimpleWavSplitter.Console.csproj
@@ -5,8 +5,8 @@
     <OutputType>Exe</OutputType>
     <GeneratePackageOnBuild>False</GeneratePackageOnBuild>
     <EnableDefaultCompileItems>False</EnableDefaultCompileItems>
-    <LangVersion>latest</LangVersion>
     <IsPackable>False</IsPackable>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/src/WavFile/SimpleWavFileSplitter.cs b/src/WavFile/SimpleWavFileSplitter.cs
index 0f7dafa..65bf129 100644
--- a/src/WavFile/SimpleWavFileSplitter.cs
+++ b/src/WavFile/SimpleWavFileSplitter.cs
@@ -15,7 +15,7 @@ namespace WavFile
     /// </summary>
     public class SimpleWavFileSplitter
     {
-        private CancellationTokenSource _tokenSource;
+        private CancellationTokenSource? _tokenSource;
 
         /// <summary>
         /// Get WAV file header.
diff --git a/src/WavFile/WavFile.csproj b/src/WavFile/WavFile.csproj
index 92ce02f..7277d6f 100644
--- a/src/WavFile/WavFile.csproj
+++ b/src/WavFile/WavFile.csproj
@@ -1,12 +1,12 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net461</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;net461</TargetFrameworks>
     <OutputType>Library</OutputType>
     <EnableDefaultCompileItems>False</EnableDefaultCompileItems>
     <GeneratePackageOnBuild>False</GeneratePackageOnBuild>
     <DocumentationFile>bin\$(Configuration)\$(TargetFramework)\$(AssemblyName).xml</DocumentationFile>
-    <LangVersion>latest</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/tests/WavFile.UnitTests/WavFile.UnitTests.csproj b/tests/WavFile.UnitTests/WavFile.UnitTests.csproj
index 1faa670..6195428 100644
--- a/tests/WavFile.UnitTests/WavFile.UnitTests.csproj
+++ b/tests/WavFile.UnitTests/WavFile.UnitTests.csproj
@@ -5,8 +5,10 @@
     <OutputType>Library</OutputType>
     <LangVersion>latest</LangVersion>
     <IsPackable>False</IsPackable>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
+  <Import Project="..\..\build\Base.props" />
   <Import Project="..\..\build\XUnit.props" />
 
   <ItemGroup>