diff --git a/tests/FreeMediator.UnitTests/FreeMediator.UnitTests.csproj b/tests/FreeMediator.UnitTests/FreeMediator.UnitTests.csproj
index 38b7327..b91af93 100644
--- a/tests/FreeMediator.UnitTests/FreeMediator.UnitTests.csproj
+++ b/tests/FreeMediator.UnitTests/FreeMediator.UnitTests.csproj
@@ -36,7 +36,7 @@
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         <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.9"/>
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.7.0"/>
-        <PackageReference Include="NSubstitute" Version="5.3.0"/>
+        <PackageReference Include="NSubstitute" Version="6.0.0"/>
         <PackageReference Include="xunit" Version="2.9.3"/>
         <PackageReference Include="xunit.runner.visualstudio" Version="3.1.5">
             <PrivateAssets>all</PrivateAssets>