diff --git a/books/free-programming-books-langs.md b/books/free-programming-books-langs.md
index c1d9f4f93..ed6e27e91 100644
--- a/books/free-programming-books-langs.md
+++ b/books/free-programming-books-langs.md
@@ -1698,7 +1698,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [MonoGame Succinctly](https://www.syncfusion.com/ebooks/monogame_succinctly) - Jim Perry
 * [.NET for Visual FoxPro Developers](http://foxcentral.net/microsoft/NETforVFPDevelopers.htm)
 * [.NET Framework Notes for Professionals](https://goalkicker.com/DotNETFrameworkBook/) - Compiled from StackOverflow Documentation (PDF)
-* [.NET Performance Testing and Optimization - The Complete Guide](https://www.red-gate.com/library/net-performance-testing-and-optimization-the-complete-guide) - Paul Glavich, Chris Farrell (PDF)
+* [.NET Performance Testing and Optimization - The Complete Guide](https://assets.red-gate.com/community/books/dotnet-performance-testing-and-optimization.pdf) - Paul Glavich, Chris Farrell (PDF)
 * [NuGet In-House Succinctly](https://www.syncfusion.com/ebooks/nuget-in-house-succinctly) - José Roberto Olivas Mendoza
 * [Rider Succinctly](https://www.syncfusion.com/ebooks/rider-succinctly) - Dmitri Nesteruk
 * [Under the Hood of .NET Memory Management](https://assets.red-gate.com/community/books/under-the-hood-of-net-memory-management.pdf) - Chris Farrell, Nick Harrison (PDF)