diff --git a/test/CommandLineParserTests/CommandLineParserTests.csproj b/test/CommandLineParserTests/CommandLineParserTests.csproj
index 51d4316..605a095 100644
--- a/test/CommandLineParserTests/CommandLineParserTests.csproj
+++ b/test/CommandLineParserTests/CommandLineParserTests.csproj
@@ -14,7 +14,7 @@
     <ItemGroup>
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.7.0" />
         <PackageReference Include="Newtonsoft.Json" Version="13.0.4" />
-        <PackageReference Include="NSubstitute" Version="5.3.0" />
+        <PackageReference Include="NSubstitute" Version="6.0.0" />
         <PackageReference Include="xunit" Version="2.9.3" />
         <PackageReference Include="System.IO.Abstractions.TestingHelpers" Version="22.1.1" />
         <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
diff --git a/test/ConfigurationTests/ConfigurationTests.csproj b/test/ConfigurationTests/ConfigurationTests.csproj
index f1e1ccf..530fe2d 100644
--- a/test/ConfigurationTests/ConfigurationTests.csproj
+++ b/test/ConfigurationTests/ConfigurationTests.csproj
@@ -13,7 +13,7 @@
     <ItemGroup>
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.7.0" />
         <PackageReference Include="Newtonsoft.Json" Version="13.0.4" />
-        <PackageReference Include="NSubstitute" Version="5.3.0" />
+        <PackageReference Include="NSubstitute" Version="6.0.0" />
         <PackageReference Include="xunit" Version="2.9.3" />
         <PackageReference Include="System.IO.Abstractions.TestingHelpers" Version="22.1.1" />
         <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">