diff --git a/books/free-programming-books-langs.md b/books/free-programming-books-langs.md
index db8a55726..588d590d5 100644
--- a/books/free-programming-books-langs.md
+++ b/books/free-programming-books-langs.md
@@ -533,7 +533,7 @@ Books on general-purpose programming that don't focus on a specific language are
 * [C++ Succinctly, Syncfusion](https://www.syncfusion.com/resources/techportal/ebooks/cplusplus) (PDF, Kindle) (email address *requested*, not required)
 * [C++ Tricks](http://www.bordoon.com/cplusplus/book_wrapper.html)
 * [C++ Tutorial](https://www.cprogramming.com/tutorial/c++-tutorial.html) - Alex Allain
-* [CS106X Programming Abstractions in C++](http://web.stanford.edu/class/cs106x/)
+* [CS106X Programming Abstractions in C++](https://web.stanford.edu/class/cs106x/)
 * [Elements of Programming](http://elementsofprogramming.com) - Alexander Stepanov, Paul McJones (PDF)
 * [Essential C++](https://www.programming-books.io/essential/cpp/) - Krzysztof Kowalczyk, StackOverflow Contributors (CC BY-SA)
 * [Financial Numerical Recipes in C++](https://ba-odegaard.no/gcc_prog/recipes/) - Bernt Arne Ødegaard (PDF)