diff --git a/Reihitsu.Cli.Test/Reihitsu.Cli.Test.csproj b/Reihitsu.Cli.Test/Reihitsu.Cli.Test.csproj
index 73f1f368..321ad2d3 100644
--- a/Reihitsu.Cli.Test/Reihitsu.Cli.Test.csproj
+++ b/Reihitsu.Cli.Test/Reihitsu.Cli.Test.csproj
@@ -9,7 +9,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.7.0" />
     <PackageReference Include="MSTest.TestAdapter" Version="4.3.2" />
     <PackageReference Include="MSTest.TestFramework" Version="4.3.2" />
-    <PackageReference Include="NSubstitute" Version="5.*" />
+    <PackageReference Include="NSubstitute" Version="6.*" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="5.6.0" />
   </ItemGroup>