diff --git a/exercises/testing-code/solution/Tests/TemporalDurableExecution.Tests.csproj b/exercises/testing-code/solution/Tests/TemporalDurableExecution.Tests.csproj
index 6b567fd..05a8eff 100644
--- a/exercises/testing-code/solution/Tests/TemporalDurableExecution.Tests.csproj
+++ b/exercises/testing-code/solution/Tests/TemporalDurableExecution.Tests.csproj
@@ -20,6 +20,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="System.Text.RegularExpressions" Version="4.3.1" />
     <ProjectReference Include="..\Workflow\TemporalDurableExecution.Workflow.csproj" />
   </ItemGroup>