diff --git a/Functions.Tests/CoffeeMonitor.Functions.Tests.fsproj b/Functions.Tests/CoffeeMonitor.Functions.Tests.fsproj
index 95546e7..0f38a5f 100644
--- a/Functions.Tests/CoffeeMonitor.Functions.Tests.fsproj
+++ b/Functions.Tests/CoffeeMonitor.Functions.Tests.fsproj
@@ -17,7 +17,7 @@
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-    <PackageReference Include="NSubstitute" Version="4.1.0" />
+    <PackageReference Include="NSubstitute" Version="4.2.1" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>