diff --git a/docs/diagram.md b/docs/diagram.html
similarity index 100%
rename from docs/diagram.md
rename to docs/diagram.html
diff --git a/docs/index.md b/docs/index.md
index b28a64bc..49f01bb4 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -18,7 +18,7 @@ How it works
 This diagram summarises the steps that cibuildwheel takes on each platform to build your package's wheels.
 
 {%
-   include-markdown "diagram.md"
+   include "diagram.html"
 %}
 
 This isn't exhaustive, for a full list of the things cibuildwheel can do, check the [options](options.md) page.