diff --git a/tests/Prometheus.Client.HttpClient.Tests/Prometheus.Client.HttpClient.Tests.csproj b/tests/Prometheus.Client.HttpClient.Tests/Prometheus.Client.HttpClient.Tests.csproj
index 09528a9..774bb2a 100644
--- a/tests/Prometheus.Client.HttpClient.Tests/Prometheus.Client.HttpClient.Tests.csproj
+++ b/tests/Prometheus.Client.HttpClient.Tests/Prometheus.Client.HttpClient.Tests.csproj
@@ -8,7 +8,7 @@
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     <PackageReference Include="FluentAssertions" Version="6.12.1" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
-    <PackageReference Include="NSubstitute" Version="5.1.0" />
+    <PackageReference Include="NSubstitute" Version="5.3.0" />
     <PackageReference Include="xunit" Version="2.9.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
       <PrivateAssets>all</PrivateAssets>