In 5.0.0 release notes: Upgrade log4net to v2.0.13 (@jonorossi, @stakx, @dschwartzni, https://github.com/castleproject/Core/pull/574, https://github.com/castleproject/Core/pull/605) Yet log4net doesn't appear in dependencies on this page: https://www.nuget.org/packages/Castle.Core Here is the reference: https://github.com/castleproject/Core/blob/master/src/Castle.Services.Logging.SerilogIntegration/Castle.Services.Logging.SerilogIntegration.csproj