diff --git a/chapters/ch01-test-doubles/Ch01.TestDoubles.csproj b/chapters/ch01-test-doubles/Ch01.TestDoubles.csproj
index 02aaa03..222f6ce 100644
--- a/chapters/ch01-test-doubles/Ch01.TestDoubles.csproj
+++ b/chapters/ch01-test-doubles/Ch01.TestDoubles.csproj
@@ -11,7 +11,7 @@
     <PackageReference Include="AwesomeAssertions" Version="9.4.0" />
     <PackageReference Include="coverlet.collector" Version="6.0.4" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
-    <PackageReference Include="NSubstitute" Version="6.0.0" />
+    <PackageReference Include="NSubstitute" Version="6.1.0" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
   </ItemGroup>