diff --git a/content/downloads/notebooks/BufferProtocol.ipynb b/content/downloads/notebooks/BufferProtocol.ipynb
index e8702bd..05ae531 100644
--- a/content/downloads/notebooks/BufferProtocol.ipynb
+++ b/content/downloads/notebooks/BufferProtocol.ipynb
@@ -217,7 +217,7 @@
    "source": [
     "Before you go on, you should know that this topic is fairly advanced as far as Python tutorials go, and requires more background knowledge than the average Python hacker probably has.  To get started, I'd take a look at the following resources:\n",
     "\n",
-    "- [Python Modules in C](http://dan.iel.fm/posts/python-c-extensions/): a tutorial by Dan Foreman-Mackey. This is a great first intro to writing C-API code.\n",
+    "- [Python Modules in C](https://dfm.io/posts/python-c-extensions/): a tutorial by Dan Foreman-Mackey. This is a great first intro to writing C-API code.\n",
     "- [Defining New Types](https://docs.python.org/3/extending/newtypes.html): an excellent tutorial from the official Python documentation. This goes through the basics of creating a type (a class) using C, which can then be visible in Python.\n",
     "\n",
     "If you get through these tutorials, the following links serve as a really handy reference on the Buffer Protocol itself:\n",